Many of us learned about ecosystems in grade school; tundras vs taigas, temperate forests vs rainforests, freshwater vs marine systems, etc. An ecosystem consists of living, interacting organisms and their environment, and a defining principle is that change in one portion of the system will result in change elsewhere in the system. This has been observed countless times in nature and in real and virtual simulations of natural environments. 

The goal in creating an aquarium should not be to simply fill a tank with water and add your desired inhabitants. Imagine someone filled a box with air (and maybe a few rocks) and placed you inside it. You would survive (for a little while), but your quality of life would be pretty subpar to say the least. All life on this planet is similar in that we rely on other each other in some way in order to survive. The more species you have working together to fill all the niches of that system, the more stable it will be. This is one of the basic principles of ecology; increased biodiversity leads to increased stability. The same principle applies to our aquariums.

In any of our shrimp tanks (all of which are 10 gallons or less), there are at least a dozen (usually more) different species of flora and fauna visible to the naked eye. If you were to examine the tank under a microscope, you would find hundreds if not thousands of different types of microbes (largely residing in the substrate and filter media) which are all performing vital processes in the tank. In saltwater aquariums this number increases exponentially. Establishing a healthy microbiome in your tank is vital if you want to maintain stable parameters (more on this in the ‘Set Up’ section).

We work as part of a team that actively monitors the health of artificially created marine ecosystems (meant of offset ecological damage) along the California coast. In our free time, we create our own miniature ecosystems at home as this brings us joy :), and we feel we are sparing our inhabitants from a less desirable life at the pet store or in a plastic filled tank. Over the past few years, we have picked up various tricks and useful bits of information which we have decided to conglomerate into one (hopefully complete) guide, as this is something we were never able to find. Here, we will include much of what we've learned about creating and caring for a miniature aquatic ecosystem and what we wish we knew when we started. 

Now, where to begin? 

Ah yes, as with all things.

How big should my aquarium be?

That depends entirely on your physical size constraints (table space/room size), available funds ($$$), and what you want to keep in the tank (in THAT order!). Larger tanks (obviously) can hold larger inhabitants and are generally easier to create a stable environment in as they tend to require less frequent maintenance, while smaller tanks can be finicky and often require more focused care. For this guide we will focus on smaller tanks (<10 gallons), as these can be more appealing to newcomers (less $$$) and often pose interesting and unique challenges based on the desired setup. 

First things first, if you have specific species you want to incorporate into the system you should look up their respective tank size requirements before deciding your tank size, as that is far too much information to include here (that’s a good rule for many of the criteria we will be discussing).  

A common ‘rule’ you may hear thrown around is 1” of fish per 1 gal of water. Hence a 5 gallon aquarium could hold five 1” fish or one 5” fish. This is bullshit. Different fish require different size parameters based not only on their physical size (biomass approximated by length), but also their individual and social behaviors (are they schooling, are they bottom dwellers, do they require more vertical space or horizontal space, etc.). Larger groups of smaller fish (certain guppies, tetras, rasbora) can often be kept in smaller tanks than smaller groups of larger fish (sharks, loaches, gourami). Invertebrates (shrimp, snails) require far less space than most fish of the equivalent biomass largely because they tend to feed on an entirely different trophic level of prey and do not contribute the same level or type of waste as vertebrates.  

The smallest stable tank we have created (and maintained for a prolonged period of time) is in a 1/2 gallon glass cube. Only a few cherry shrimp, 1 nerite snail, and a couple aquatic plants/algae inhabit this tank. Because of its low bioload, it only requires bi-monthly water changes, weekly replenishment of evaporated water, and a basic pump filtration setup to maintain stability. 

Essentially: bigger isn’t always better but it’s usually easier, but more importantly: live within your means.

Okay, what about the shape of the aquarium?

Shallower tanks tend to have a wider footprint and are a good choice if you want bottom feeders like plecos, catfish, ottos, etc. Taller tanks provide greater water depth and are a good choice for mid-high water column fish like tetras and guppies. Curved tanks can distort your perspective of the interior, causing its inhabitants to appear larger than they actually are. While this may be appealing for some, curved tanks can cause disorientation for tank inhabitants (more applicable to fish than invertebrates); increasing stress and ultimately reducing their lifespans :(. Curved tanks (spheres, specifically) also tend to have less surface area at the top of the tank for gas exchange between the water and air. If you purchase a spherical tank, consider reducing the water level of the tank to maximize water surface area.

Glass tanks will ultimately last longer than acrylic tanks, though acrylic tanks will appear clearer (at first, then they turn yellow over time). If you purchase a glass/acrylic scrubber make sure it matches the material of your tank or you will get many many scratches.

It is also important to properly inspect any tank you purchase (especially if you’re purchasing a used tank) and ensure it holds water to the desired level without leaking. The silicone that connects the panels of a tank will ultimately wear out overtime and this is much easier to repair BEFORE the tank is set up. 

There are a few key pieces of equipment that you will need depending on what is inhabiting your tank, this includes the tank (duh), a suitable light, and a filtration system. Water filters not only clean the water in your tank, they also induce water movement which is essential for properly aerating the system and preventing toxic O2 or CO2 build up. The different layers of the filtration system provide an excellent media in which essential microbes will live (aside from your substrate). Though some may disagree, I have found that including a filter in your set up is vital in maintaining stable water parameters - especially in a small aquarium (unless you plan on only having aquatic plants, or are comfortable performing frrequent water changes). 

Other important (but not necessarily vital) pieces of equipment include a heater, air bubbler, water pump, thermometer, CO2 system, and water quality test kit. Substrate and decor will be included in the ‘Set Up’ section. I will explain the importance of these pieces of equipment below.

Light

A light is important for both the flora and fauna inhabiting your tank. Plants and algae use light to perform photosynthesis (a vital process as this will increase the partial pressure of oxygen in the tank). When the light is turned off your plants will also perform respiration, thus producing carbon dioxide. During this process, plants and algae will remove certain nutrients (nitrates) from the soil and water column which would otherwise be harmful to fish and invertebrates. Fish and other fauna require a light source that is turned on and off for a set period of time on a daily basis to maintain their circadian rhythms - without such a light they will become overly stressed and may not be able to adequately regulate their immune systems, resulting in premature death. Though you can use sunlight as a natural light source, this is generally not recommended as it is harder to regulate (think about cloudy/rainy days) and requires the tank to be in close proximity to a window, which can cause adverse temperature fluctuations in the tank. If you have an acrylic tank, sunlight will increase the rate at which the tank walls yellow. Artificial lights should be kept on for 8-12 hours a day (depending on your setup). Some of these lights have a built in timer which makes maintaining proper doses of daily lighting significantly easier, especially if you have a busy/variable work schedule. You can also purchase a plug in  If you notice excessive algal growth in your tank, you should reduce the amount of light your tank recieves on a daily basis.

Filter

As I said before, filters not only remove unwanted compounds from your aquarium, they also increase water flow, which in turn increases the surface area of water coming in contact with the air. This will significantly aid in off-gassing dissolved gasses like CO2 and O2 depending on what is building up in your tank. 

Freshwater filters typically come in 2 main categories; sponge filters (more basic) and carbon (chemical) filters (more advanced). Sponge filters consist of a water pump with an inlet covered by a fine sponge - this traps larger particles suspended in the water column and provides a home for beneficial bacteria to live in, which will aid in removing ammonia and nitrites from the water. Carbon filters consist of a water pump that passes water over a carbon media - this also provides a home for bacteria and generally does a better job of removing unwanted compounds from your tank’s water, at the cost of being bulkier, more expensive, and requiring the carbon media to be replaced on a semi-regularly basis. Sponge filters typically live in the tank and can often be fully submerged, while carbon filters remain partially submerged and often hang off the back/side of the tank. Carbon filters can also be entirely separate from the tank, with only input/output tubes connecting them to the tank (this is generally desired for larger builds). The right filter for you depends entirely on your set up, though I will say sponge filters are usually adequate for smaller tanks - especially those without larger inhabitants. 

Heater

Many pet stores market heaters as a vital component of your tank set up. This depends entirely on your tank inhabitants and your location. Certain species of fish (especially tropical fish) prefer warmer water and will likely benefit from the stability in temperature provided by an in tank heater. If you only plan on keeping invertebrates (shrimp, snails) and plants in your tank you do not necessarily need a heater (in fact many of these species prefer colder water and will breed more readily in such). If you live in an area where the temperature is consistently warm year round you likely do not need a heater (not to say your tank wouldn’t benefit from one). If you do purchase a heater you should match the heater’s power output to the size of your tank. Adjustable heaters are always better than preset heaters (though more costly). 

Thermometer

An important, often overlooked piece of equipment for your tank - especially if you don’t have a heater. Keeping a thermometer in your tank will allow you to consistently measure water temperature and keep an eye on temperature fluctuations which may adversely affect your tank inhabitants. Keep in mind placing the thermometer directly next to your heater or in direct sunlight will create bias in the temperature readings. 

Air Bubbler

Air bubblers pump atmospheric air into your tank (generally through porous air stones) which both increases water movement in the tank and will increase the partial pressure of oxygen in the water. Though smaller tanks do not need them, a bubbler will almost always be beneficial to the critters inhabiting your set up (regardless of your tank size), and may significantly improve the quality of life for many of your tank residents. When setting up a bubbler in your tank, ensure the airstone is as close to the substrate as possible to maximize the amount of O2 that may diffuse into the water column. Keep in mind air pumps are inherently noisy - you may want to have them on a timer (especially if your tank is near where you sleep).

**Bubblers should not be used as a replacement for live plants in your tank

Water Pump

Water pumps function by circulating water throughout your tank. Though they should not be used as a replacement for a filtration system, they can aid in increasing water flow in your tank - especially if you have inhabitants that prefer fast moving water. Water pumps can be combined with sponge material to create a makeshift sponge filter - just ensure all inlets of the pump are protected by the sponge or you will get large particles in the pump which will gum it up over time. 

Water Quality Test Kit

I debated including this in the “vital” portion of tank equipment, though I suppose you can maintain a stable tank without it - it will just be much harder. A decent water quality test kit should include tests for pH, Nitrites, Nitrates, Hardness, and Alkalinity. More advanced kits may also includes tests for Chlorine, Ammonia, and Sodium Chloride. All of these are vital parameters which can seriously effect the health of your tank inhabitants if they are out of balance; being able to determine which parameter(s) are out of balance is key to determining how to return your tank to a more stable state. Performing water changes with filtered water will almost always increase the health of your tank inhabitants if they are displaying symptoms of poor health, however many filters are not be able to filter out all of the above molecules which is why having one of these kits is so important in maintaining tank health. A test kit can also help you decide when your new setup is ready for inhabitants (more on this in a moment). 

CO2 System

CO2 systems function similarly to an air pump, except they diffuse CO2 into the tank instead of air. This can be extremely beneficial in promoting plant growth (it will increase the rate of photosynthesis provided there is sufficient light/nutrients for the plants), but can be detrimental to any animals you have in the tank. As CO2 diffuses into the water it will bond with water molecules to create carbonic acid (H2CO3). This will break down into Hydrogen ions (H+) and bicarbonate ions (HCO3-). The increased concentration of hydrogen ions will lower the pH, thus increasing the acidity of the tank. (This is the same process by which increased CO2 pollution in the atmosphere is increasing oceanic acidity). This can become harmful to animals (especially fish and calcium-dependent invertebrates) extremely quickly, as they are much more susceptible to rapid fluctuations in pH than plants and algae (note some species are more sensitive than others). If you add a CO2 system to your tank, be sure to meter it extremely slowly (like the lowest possible level at first) to ensure you do not cause a rapid change in pH in your tank. Be sure to monitor your tank as often as possible for signs of poor health of its inhabitants. 

Of the many potential inhabitants of a small freshwater ecosystem, aquatic shrimp are, obviously, the most applicable to this site (and we think the cutest:), therefore this is where we will spend the most time. 

There are a variety of differently colored and shaped small freshwater shrimp, though they generally fall under 2 main genera; Neocaridina abd Caridina. Within Neocaridina there are a couple different species, including N. davidi and N. palmata - both popular in the aquarist community. By far the most prominent and diverse specie at pet stores will be N. davidi, which has many different sub-phenotypes (referred to as morphs). Some of the more common ones include Red Cherry, Blue Dream, Yellow Goldenback, Green Jade, Black Rose, Red Rili, Carbon Fiber, and many more. Though these morphs may differ dramatically in apperance, it is important to note that as they all fall under the same specie, they can all mate with eachother (speciation 101). Breeding different morphs can produce unusual and even beautiful results, though the vast majority of the time the colors will combine to form some sort of brown or colorless shrimp (or somewhere in between). This can be especially frustating if you are trying to maintain a specific color in your tank to contrast or compliment some other feature (ask us how we know). 

N. palmata includes the popular Blue/White Pearls, among others. Though there have been cases of N. davidi and N. palmata breeding, the offspring are usually not viable/not fertile (hence the species distinction). Inbreeding is generally a problem in small mammalian circles as it results in a increased number of genetic mal-mutations, but this does not seem to be an issue in small aquatic invertebrates. Growing a large/stable population from a few individuals should not increase the amount of genetic weaknesses in the population. 

The other main genus of shrimp (for small aquariums) is Caridina. This genus includes species such as C. multidentata (Amano shrimp), C. cantonesis (Black and Red Crystal shrimp) , and C. mariae (Tiger shrimp). Like Neocaridinas, Caridinas display high morphological variation with related morphs cabale of interbreeding. Cardinia are generally more susecptible to change in water parameters than Neocardina, and are often less compatible with other vertebrates as they require colder, more acidic water. Additionally, Caridinas are more succeptible to TDS (total dissolved solids) and will greatly benefit from a high quality (preferrable RO) water filter (many in the shrimp-world would call this necessary). 

Below are basic water parameters forthe most common aquarium shrimp, be sure to research your specific species/morph before setting up your tank!

Neocaridina davidi: 

Optimal water temp: 68-81F

Optimal pH: 6.5-8.0

Optimal TDS: 100-300ppm

Caridina cantonensis: 

Optimal water temp: 64-75F

Optimal pH: 5.5-6.5

Optimal TDS: 80-160ppm

Caridina multidentata:

Optimal water temp: 62-82F

Optimal pH: 6.5-7.5

Optimal TDS: 100-300ppm

Atyopsis moluccensis: (Bamoboo Shrimp)

Optimal water temp: 72-82F

Optimal pH: 6.5-7.5

Optimal TDS: 100-200ppm

Caridina dennerli: (Sulawesi Shrimp) **Will require extremly focused care

Optimal water temp: 81-86F

Optimal pH: 7.5-8.5

Optimal TDS: 150-200ppm

Of course, shrimp aren't the only cute inhabitants you can create a home for. Many smaller species of fish are suitable for a small aquarium (including rasbora, tetras, guppies, etc.), as are other invertebrates (primarily snails). Creating a balance between different types of organisms that prey on different trophic levels of food is key to creating a functionally stable tank. You should research the specific species you are contemplating adding to your tank and consider the follow: what parameters (water quality/temperature, light [wavelength/intensity/duration]) that species requires as well as what other species it can interact positivly with. 

*Shrimp occupy a lower level in the trophic web and are preyed on by many larger vertebrates - keep this in mind if you are thinking of adding both to your tank. (they may also be preyed on by other invertebrates, i.e. assasin snails). 

When choosing inhabitants for your tank you should be less concerned with how they will look together aesthetically and more concerned with what niche they will occupy. Having many species of vibrantly colored fish may be appealing, but you most consider that they are all occupying the same effective niche (there is only so much room for variation in niches {which I am hereby dubbing 'nichiation'] in a 10 gal. or less tank) and likely will not be able to coexist in a stable setting for prolonged periods of time unless given constant and close attention. 

The basic niches in any properly set up tank should include an open water zone (ideally occupied by mid-high water column fish), a benthic zone (ideally inhabited by a combination of bottom-dwelling fish and invertebrates [shrimps, snails]), and vegetated zones (which create sheltered areas for shrimp and small fish as well as providing increased surface area for microbial life). 

Of course, creating a functional ecosystem relies on both heterotrophs (organisms that consumer other organisms - what we have been discussing!) and autottrophs (organisms that make food from light engery - plants and algae [which for those of you wondering are very distinct]). Do not neglect plants in favor of interesting looking animals when setting up your tank - if anything plants should be your priority (algae will grow naturally, unless you're using highly chlorinated water - don't do that.

Setting up an aquarium can be a surprisingly lengthy process, especially if you don't have access to a mature freshwater tank. Because your new tank will not have a preformed microbial system in the substrate, filter media or water column, before adding animals (fish, shrimp, snails, lobster) to your aquarium you must allow it to run through the nitrogen cycle. This will effectivley build the bacterial system necessary to convert highly toxic ammonia (NH4+)  (created by nitrosonomas bacteria decomposing fish waste, decaying plants, and excess food) into nitrites (NO2-). Nitrospira bacteria then convert the nitrites into nitrates (NO3-) which can be absorbed by living plants and algae (and is essentially fertilizer). There are two key components to this process (aside from the equipment previously discussed); Substrate, and plants. 

The right substrate for you tank is determined by the size/shape of your tank, the style you want, and your tank's inhabitants. Finer (sand, gravel) or porous substrates (volcanic rocks) will promote greater surface area for microbial growth. Finer substrates are generally a more suitable substrate for rooted plants than larger rocks, but it can be benefitial to use a combination of the two. Ideally your substrate would include some form of fertilizer for your plants (this will be especially useful in establishing your aquarium devoid of larger vertebrates). Your substrate will be most easily scaped if placed in the tank before it is filled with water; allowing the substrate to soak for a day or two before placing it may help prevent loose material from floating to the surface. 

Similarly, the right plants for your tank are based on its size, desired style, and inhabitants. Carpeting plants like Micranthemum, Elocaris, and Monte Carlo are popular with aquascapers as they can produce a full, aesthetic look and provide a good habitat for small benthic fish and invertebrates such as bottom-dwellers and dwarf shrimp. Mosses like java moss or christmas moss tend to grow very quickly and provide an excellent habitat and breeding ground for dwarf shrimp. Larger plants are generally placed towards the back of the tank with increasingly smaller ones' planted closer to the front in order to give off the illusion of depth. It can be helpful to have the subsrate raised in the back with a slope lowered in the front to give your scape the same effect.

Having a diverse (but relativley small) community of plants and algae in your tank when you add water (before you beginning the nitrogen cycle) will actually increase the speed at which the process occurs. You may experience some plant mortality - especially if you do not encorporate some sort of fertilizer into your soil. However die back of existing leaves is normal to the acclimation process, as the plant goes from airid growth to aquatic growth. At this point in your initial setup, even though you don't have animals in the tank, you should still feed the tank with fish food - not a lot, just enough the kickstart the cycle. 

Here's a rough breakdown of how the process will be carried out in your tank:

1) Waste (food waste, decaying plant matter, fertilizers) will breakdown, causing an ammonia spike in the tank - this can happen within hours to days of setting up your tank.

2) As Nitrosomonas bacteria build up in your filter media, ammonia levels fall off sharply and nitrite levels spike. These nitrifying bacteria prefer warmer water (optimal temp 86F) and can multiply at a rate of 2x every 7 hours under ideal conditions. Growth rate 0.5x at 64F, growth rate 0.25x at 50F. The optimal pH for nitrifying bacteria is between 7.3 and 8.0.

**All nitrification will stop at pH's below 6.0 = special concern for CO2 diffusion systems

3) Nitrate levels with gradually rise while nitrite levels fall, signifying the presence of a healthy population of nitrobacteria to balance the population of nitrifying bacteria.

4) Over time, nitrate levels will need to be balanced by water changes, autotrophs, and a filtration system. Detecatable nitrate levels should remain just above zero. There should be no detectable nitrite levels. Your tank may go through multiple cycles of ammonia, nitrate, and nitrite spikes; it is wise to wait to add animals (especially fish) to your tank until after these swings have stabilized - this will take 1-3 weeks. 

**You can jump start this process if you have access to a mature (fully cycled) tank; adding water/substrate from that tank to your new aquarium will provide a more complete initial colony of bacteria and will reduce the total amount of time needed for the tank to cycle. You should still wait to add animals until after nitrogen levels in the tank have reached a stable state. Keep in mind if you add water from another mature tank, you may accidentally transfer unwanted pests to your new tank, which can be very hard to remove once they are established.

Okay, cool you got your tank set up! Now, how to take care of it? 

This is very dependent on the size of your tank, your filtration setup, your inhabitants, and how often you feed them. As stated before, smaller tanks typically require more frequent maintinence as there is simply less space for plants and algae to grow and remove harmful compounds from the system. Anything less than 5 gallons should be cleaned (or at least test the water parameters) on a weekly/bi-weekly basis. With 5-10 gallons you can generally get away with bi-weekly/monthly cleanings. You should rinse out your filtration system (and replace carbon filters if necessary) during these cleanings to ensure proper water flow/filtering ability. Ideally, the water level should be drained to at least 50% of total capacity and refilled with fresh, filtered water. Adding dechlorinators can be helpful if your filtered water still has high chlorine levels. The best way to remove water from the tank is with a siphon which will allow you to suck up excess animal/food waste from the substrate (be careful not to vaccumm and shrimpies!). The glass walls (interior & exterior) should also be cleaned when you clean your tank to improve aesthetics.

Your feeding schedule/what food you use is, again, entirely dependent on your inhabitants. Research the needs of your desired fauna before setting up your tank. Pretty much all aquatic creatures (that I've encountered) prefer frozen food (brine shrimp, bloodworms, etc) over pellets or flakes, but are more of a hassle to store and use. Be careful not to overfeed, if you are seeing lots of uneaten food on the substrate after feeding, consider reducing the amount of food you use. Feeding should also be on a relativly set schedule - constantly changing the time of day you feed can screw with the circadian rythynms of many animals which will in turn lead to excess stress. Automated feeders can be useful tools for when you are away from your tank, but its best not to rely on them for everyday feeding - a human touch always works better. 

There's really not much more you need to know (aside from inhabitant-specific information). I hope this hobby brings you as much joy as it does us!

• 'When in doubt, test it out' (if you suspect something is off balance in your tank, your primary step should be performing a water quality test - if for nothing more than to confirm your water parameters are within spec allowing you to consider other culprits).

• Shrimp breed extremely quickly (relative to other animals), you can grow your population from a few individuals to dozens in just a few months with the proper setup.

• Dwarf shrimp will breed more readily in colder waters (refer to parameters above), adding a dose of shrimp nutrients (available at most pet stores) really gets them excited ;)

• Lots of hiding places (plants, moss, rocks, caves, logs) will provide shrimplets a good shelter to hide in and will reduce the likelihood of them being eaten by co-inhabitants (java moss is exceptionally good at this but it will grow out of control quite quickly).

• In order to successfully breed shrimp you will need males and females (something not all aquarium store attendants can differentiate between). Females tend to have more arched/wider/rounder abdomens while males take on a more streamlined appearance and are generally slightly smaller (and sometimes less colorful). Males are generally less common than females (from our experience).

• Something will go wrong. Something always goes wrong, whether its an algae bloom, or an ammonia spike, or your filter suddenly decides to stop working, or whatever. I promise you aren't the first person to deal with that issue - a quick google search will provide you lots of helpful tips on how to remedy the situation. Don't give up on it!