Selecting Fish for best Aquaponic results

Selecting the best Fish type for Aquaponics

 As we begin to look at suitable fish for Aquaponics, let us first look at the issue of what we need to achieve in order to be successful and why fish are so important to our proposed Eco System.

If you recall fish are used in order to create a source of nutrition for the plants in our eco system because their excreta “poop” which with its “nitrites” interacts with bacteria to produce “nitrates” which are easily absorbed by plants as their favorite food as the water is cycled continuously through the whole connected system to create an eco system.

So whilst fish are fish and basically all do the same thing namely, “poop” we need to consider some selection criteria for the type of fish chosen to live and thrive in the Eco System.

Issues such as water temperature, pH and the amount of oxygen in the water become serious issues to consider.  We mention water temperature first because (unless you maintain an air-conditioned room for your tanks – which is impractical and unnecessarily expensive) you need to consider the local environment – what is the highest and lowest usual temperatures experienced in the area in which the tanks/system will operate.  By applying + and –  five (5) degree to the temperature range we can select fish that should be suitable for the local area.

As a young child I was not too keen to eat fish because on several occasions I had a bone stick in my throat so I have a preference for larger boned fish (which do not cause this problem for young children) and is very tasty to eat.

You will need almost no experience (except these notes) to select and maintain your fish as you help them to build an Aquaponic Eco System, however, the first important note is to be aware that tap water (from almost anywhere in the world) contains FLUORIDE and FLUORIDE IS A KILLER OF FISH.

To provide a suitable answer you will need to retain the water in a separate system tank (that is not connected to other tanks) for several days BEFORE you pass this water into your eco system otherwise you will most likely kill most, if not all, of your fish stocks because fish are easily killed by exposure to the chemical fluoride (which had been added to the drinking water).

Choosing what fish species to stock

Obviously if you are going to eat the fish, you will need to ensure replacement fish of the same species will be avail whenever you need to re-stock – so now we have determined that temperature (climate) and stock supplies will be important factors in your choice.  Small young fish are known as “fingerlings”.

In addition you will need to check with your local Fisheries Authority to determine if certain fish species are not permitted to be stocked in your Country or Local Area. For example, probably the most popular fish species in Aquaponic systems might be TILAPIA, however, this species is illegal in Australia because there is much concern in Australia should this species be released into waterways as they quickly overtake other species and dominate local waterways.

There is “no best fish” to select as it depends on availability and suitability to your area especially temperature climate issues. Consider – tolerance to Ammonia, ability to eat pellet foods, ability to survive in a tank eco system (and if inclined to eat other fish keep in a separate tank – see later).

Recommended list of Aquaponic Fish – these need to be FRESH WATER FISH


TROUT (especially Rainbow Trout) Trout



No doubt you have seen many TV programs about the life of wild trout fish in estuaries and streams. Because these waterways are part of natures Eco Systems you can know that Trout fish will be suitable for your Eco System. Trout species are a good choice for colder climates as they do not get distressed with cooler water temperatures. Fresh water Trout tolerate water temperatures from 8° degrees through to 22 degrees (or 50 F to 68 F) but require the water to be well oxygenated (remember trout streams run over rough ground which introduce oxygen through bubbling).

Trout are predators (carnivorous) so they need to be kept separated from other species if to be used in the same eco system.   Trout can be separated within the same eco system by the use of wire netting which allows water to pass through yet small fingerlings and other fish cannot enter or pass through into the Trout tank. Trout are well known as extremely popular fish to eat and have a quick growth rate.

In certain locations, Perch fingerlings are difficult to obtain so if you are eating your fish stock enquire when fingerlings are available – often only available in late spring or early summer months.


TILAPIA (a species variation of the Chiclid family) as mentioned above, is a very popular freshwater fish within the Aquaponic community because they are low fat and extremely tasty, hardy, quick to breed and can handle a wide range of water quality situations except they do not like colder climates as warmer temperature is their preference (so if you live in a cold climate you would need to heat the water).

Tilapia thrive on food pellets and just love to eat worms (refer to note late in this site about worms, turtles, snails and sprays).

Tilapia are available in most locations, with almost a limitless supply of fingerlings (young fish are known as “fingerlings”) available throughout the year. Usually purchased when about 3 – 4 inches in length.   They take about 9-12 months to grow to about 300 grams – a suitable size to be eaten.



Crappie (also known as Calico Bass and Kelp Bass)

This fish species is a freshwater fish well know inNorth Americaas a popular game fish.

Unfortunately they are known as predators (feeding on smaller species including their own young).

They are less active during the day and like to feed early morning or night and prefer to live around sheltered areas with submerged objects and plant beds being suitable to hide them.

Crappies are tolerant of even frozen waters and are considered as among the best tasting freshwater fish.

Be aware that Crappies are slow to reproduce (approximately as long as 2 years) and as mentioned earlier act as predators. The answer to enjoying this species in your eco system, is easily solved if you provide a separate tank to hold this species separated from fingerlings (small younger fish), and karma seems to have entered the fish world because other larger fish like to act as predators and eat Crappies.  This separation can be achieved by the use of wire netting which allows water to pass through yet small fingerlings and other fish cannot enter or pass through into the Crappies tank.



Not the prettiest fish to look at, but certainly tasty is the Catfish.

They seem to breed very quickly and are fast growers and are temperature hardy. They are widely farmed in Aquaponic settings and liked by farmers because they are well know as “great poopers” (well that is one way to get a reputation) – so you get a good conversion rate of waste to nutrients.

Catfish do not have scales, so they need to be skinned just like you would a rabbit.

In certain locations, Catfish fingerlings are difficult to obtain so if you are eating your fish stock enquire when fingerlings are available – often only available in late spring or early summer months.




These little blighters are carnivores which mean they like to eat live fish which can get expensive, however, they are regarded as a good fish for organic living especially since they are reported to have the highest levels of omega 3 oils of all suitable Aquaponic fish species.

Some people do not like the “high oily taste” so go for some “taste tests” before you decide to stock them (there are some attempts to breed a lower oil content), certainly omega 3 oils are reported to be good for your heart etc.

In certain locations, Perch fingerlings are difficult to obtain so if you are eating your fish stock enquire when fingerlings are available – often only available in late spring or early summer months.


Silver Perch are also known as Silvers, Silver Bream, Bidyan, Black Bream, Grunter and Murray Perch.


Jade Perch are a hardy, omnivorous species capable of rapid growth on relatively inexpensive diets.




Need photo


Need warm waters as this is their grow time (tropical water / climate appeal). Require little husbandry except they will eat fingerlings – so keep separate tanks.




Carp have a reputation for being extremely good at breeding and are known as an unwanted pest in many indigenous rivers where they have caused much harm to original species as well as the environment (especially the River Murray inAustraliawhere it was a Government introduced species).


Many claim carp has a fishy taste, however, Asian markets are keen to take all you can supply.



If you are in anAsiacountry you will be very familiar with Koi fish as they are revered in many ways.

Certainly they are large and most decorative fish that thrive in an eco system environment.

Many aquariums found in shops and homes highlight this attractive large fish species.

Koi are good breeders but not so good at digesting foods so as a consequence they are heavy “poopers” which is just what you need for your eco system as the conversion rate to nutrients is high.





While we are looking at attractive fish we should discuss the “goldfish”.

Certainly they are most attractive, hardy and such a nice colorful display to you tanks.

They like to have the privacy of plant cover especially when breeding, which they excel at, and because they are small (and small growers) you can easily grow 8-10 goldfish in about a gallon of water.

They seem to be polite and get along with most species.

Imagine if you had an outdoor eco system with an “in” and “out” pipe placed into your home wall, so that the goldfish could be part of your eco system and provide a colorful display inside your main room.

Remember that water finds its own levels – so measure up before you attempt demolishing the wall.


How many fish is the correct quantity to maintain

Now that you have selected the species of fish (one or several species – depending on layout, separation and volume of water) – you need to decide how many fish you can stock.  Remember you will eat the fish so depletion of your stocks will occur and you will need to re-stock and allow time for growth to occur.

In addition, you need to allow sufficient swim space for EACH fish – perhaps you should allow 1 fish for every 5 gallons and then as they grow, allow a further 5 gallons for each 1 pound. Be aware also that a smaller swim space per fish will limit the fish size as fish like space as somehow a larger swim area seems to encourage growth (which means faster to the dinner plate).

Remember that the more fish you have, the more “poop” you have – so unless you have a larger quantity of grow beds to BALANCE the volume of nutrients, you will have problems, because the excess (unused by plants) nutrients can and will cause distress to the fish as your eco system will start to become unstable.


What other species can you select for your fish tanks



Obviously there are many other suitable choices for your eco system far beyond the few we mention on this site. Remember they need to be “freshwater” species, however, talk to fish stock suppliers for more ideas which might include:- fresh water prawns, mussels, yabbies and crayfish. Just be aware that some will be cannibalistic so look at our suggestions on creating isolation tanks within your eco system – this allows fully circulation of the water yet segregation of the fish stocks.

This technique enables a range of fish stocks which you can rotate through the various isolation tanks, as you deem appropriate, especially handy as some type will keep the bottom floors of your tanks clean when moved in for a short time before being moved on once more.

What foods fish like to eat

Whilst some fish do like to eat bait, food pellets are usually enjoyed by most fish although some fish do love the occasional worm or snails, however, there are some ESSENTIAL RULES to follow or else you might KILL-OFF your eco system, which means ALL the fish and plants could die very fast (refer note elsewhere in this site about worms, turtles, snails and sprays).

Generally basic food pellets from any animals or specialty Aquaponic store should be safe providers of fish foods, be wary of experimenting unless you have a small quantity of fish stock in an isolated tank.

Worms, turtles snails and sprays

Worms are amazing creatures for they do wonders for soils – remember however that Aquaponics is soil-less (so absolutely NO SOIL at all). Some people will like to place worm near plants, others like snails (but be careful as snails might like to eat your plants before they slip off into the water to look for other tastes (before they become a fish’s dinner).

Ideally it would be best to have an exposed rock within your fish tank area on which to place these worm or snails so they effectively become “only one on an island” – if you get my drift – before dinner.

Turtles also like to eat snails and need to be monitored and cleaned BEFORE introduction.

Before you add or “drop anything” into your tanks give consideration to what “that” might have experienced or been exposed to BEFORE you “drop anything in the eco system”. Become acutely aware that you do have a working live ECO SYSTEM.

What if the worm or snail carries dangerous bacteria on their body (like in a fold of their skin / shell). Were they sprayed, did they crawl over a pesticide, what have they eaten recently as it will be “pooped” shortly.

All these issues are important considerations because they will affect your Eco System – best to carefully provide for them and supervise them for several days in a separate tank BEFORE you use them in your tanks.

Whilst in this separate tank you can give them a swim in clear water to remove any bacteria or pesticide on their body, and select their food by giving crushed fish pellets or even well dampened and torn up newspapers. Perhaps your fish supplier might have (clean) corn meal or cream wheat to help purge their gut of any unexpected nasty shocks for your eco system.

Otherwise the red worm (Eisenia foetida also known as manure worm or in fishing term red wriggler) might be a tasty morsel for your larger fish.

It is also important to discuss SPRAYS.

In an eco system you should not use sprays on plant foods (even against aphids etc). The over spray will fall onto the water surface and will definitely effect your eco system and kill the fish if not the plants.

If you have significant problems, and wish to bend the rules – you could spray onto a rag or similar surface (do this well away from the water surface) – then using a small brush, dip the brush onto the sprayed surface then apply the mixture onto the leaf of the plant.

Remember to not blame me for the tarnished pesticides you might be exposing yourself and your eco system to (especially when you eat the produce) – a better way will be to do some research on “companion planting” so that the nearness of one plant will protect the other plant from pests.