Since we live in the Arizona desert, which is a hot climate, the best edible fish for us to use in an aquaponics system it tilapia. Nile tilapia, in particular, can handle warmer temperatures. This post will be dynamic – the more we learn, the more we’ll add. 🙂

Tilapia are fast breeding (up to 1500 fry/spawn) and fast growing (from six to nine months to eating size). Males grow faster than females, so commercial producers use methods to ensure all male reproduction, or to convert females to males. We home-growers don’t need to be concerned about that, though.

Tilapia are cichlids, cousins to the pet-shop ciclids, like the oscars. They are aggressive and not-so-friendly fish. Tilapia are omnivores, eating both meat and veggies. For the most part they’re herbivores, but will eat their young and other proteins. As scavengers, they like to eat dead stuff, like dead fish and fish food. They enjoy algae and water plants like duckweed.


As we’ve been working to building our breeding colony, which is a male and a handful of females, we learned that some tilapia are more aggressive than others. They can be brutal, attacking each other, biting each other, and stressing each other to the point of death. In general, they fight for power and territory.

Our Devil Woman

We currently have three females, around 4″ in length, that we’ve been able to sex once we figured that part out. One is a evil fish, and is being kept in solitary confinement because she has no social graces at all. The other two aren’t particularly friends; the larger one keeps the smaller one confined, but they aren’t actively fighting.

A fingerling among the fry

We also have around 70 others who are fry and small fingerlings. They are all in a 15 gallon tank and doing fine. What we’ve learned is that tilapia get along better in aquarium environments when they’re crowded; they can’t pick on just one so the aggression gets distributed, or just mellows out. We’ll soon be putting the largest four of these in with the two nicer females in hopes of 1.: crowding them a bit, and 2.: finding a male. These four are small enough to be difficult to sex, though we have our suspicions.

Lots of little fish. These are all Nile Tilapia.

Notice the flared fins on this female. We introduced her to two others, and none were very happy about it. When the fish are vying for territory, power, or whatever else they argue over, they take on their aggressive look. Raising and spreading out the fins makes them look bigger. When they fight, the'll push each other with their tails, dart after each other, and bite each other's sides. They can actually take the scales off another fish.


A breeding colony, as mentioned, is one male and three to five females. With females around, the male will build a nest and protect it, even against his harem. So he needs a visual barrier between him and the females. A flower pot does well for this, so I hear. We’ll let you know once we find our male.

The reason a harem is needed is because tilapia, like rabbits and chickens, will literally kill a single mate with sex. The male is quite aggressive with his desires, and giving him multiple females allows the girls to get breaks and recover.


We currently have a 29 gallon tank that will serve as our fingerling tank, and we have a 15 gallon for our fry. A little 4 gallon tank serves as an infirmary for sick fish. And of course, the 300 gallon main tank or “pond” will be the food tank. But for breeding, we’re using another 29 gallon tank. This seems crowded, but our fish aren’t too large yet, and too much room isn’t a good thing, as mentioned above.  We could put the breeders in the pond, but we want to control the conditions more. Our PH is very high here, and lowering PH in a small tank is much easier than controlling it in a large tank. We’ll see how that goes!

Types of Tilapia

There are a three main types of tilapia that are used for food. Nile Tilapia (O. niloticus” reddish to white with bars on caudal fins and white color strips on dorsal and anal fin); Blue Tilapia (O. aureus: bluish in color with red margins on fins); and Mosambique Tilapia (O. mossambicus: dark in color with no bars on fins). There are many hybrids. A popular hybrid is the Red Tilapia.

The main differences in the species are relatively minor. The age to maturity and aggressiveness aren’t significant enough to worry about in a home system, but the PH tolerance and temperature tolerance might be.  You want to raise the fish that fit your environment best.

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13 Responses to Tilapia

  1. I really like all you’re doing Sheri. You’re doing what Jay and I would like to do!

  2. David says:

    Good information. Thanks for sharing.

  3. Marc says:

    I live in the valley and my ibc aquaponics has been fine until yesterday. I had several dead fish and after checking my levels they were all fine. Is it possible some of the larger fish attacked and killed the smaller fish due to hunger? Some of the fish I pulled put appeared to have been eaten on and perhaps the ones that appeared fine had succumb to their injuries but not yet been snacked on. The water is also very murky all of the sudden but again all levels are fine. Any ideas?

    • Hi, Marc! I’m sorry I missed your post. By now I hope you have the issue resolved, but I’ll go ahead and answer anyway.
      The three primary reasons tilapia will attack each other is hunger, disease, and breeding. Hunger is possible, but if you’ve been feeding them it’s not likely. If a fish is sick, the others will pick on it and can kill it, eventually eating it typically. The most common reason, though, is that you have breeding going on, and the dominate fish are taking it out on the submissive fish. The male will stake out territory and defend it, and if the other fish are significantly smaller, he can kill them. You can give them hiding places or overcrowd your tank by adding more fish. They do settle down when there are a lot of fish to chase, oddly enough.
      As for the water issue, when you wrote this we were reaching the heat of summer, and that is the time algae loves. The warmth, light, and low oxygen in the water causes algae issues. Protect your tank much as possible from the sunlight and add as much turbulence as you can to increase the aeration. Even if you think you have enough, it might not be. In our environment even our tap water is low on dissolved oxygen!
      I’m hoping by now you’re in good shape. I’d love to hear an update, and find out what you’ve learned!

  4. Chris says:

    Hi, I have 7 tilapia but still can’t tell which is female or male. I read about it but still not clear. Any easy way to found out?

    • Chris, I can answer as it relates to Nile and Blue tilapia. Each species is a little different, but overall, this should work. Now, when they’re juveniles (before sexual maturity) it’s nearly impossible to tell. Once they reach maturity, at about 5″-6″, some people can tell by their genitalia. To be honest, it’s easier to look at their fins. The larger they get, the more obvious the differences become. Males will develop dorsal and anal fins that are pointier when spread out, and the larger the fish becomes, the longer the fin grows. Eventually, the male fin will stretch out as long as the tail. The female’s fins will be more rounded, and will remain shorter.
      Other indicators include size and behavior. Females tend to be smaller, mostly because males are more aggressive and get more of the food. 🙂 This is not a cut-and-dried rule, though. There are larger females and smaller males. With Nile tilapia, color is a strong indicator in the dominate fish; meaning the alpha male and dominate female. When mature and ready to breed, females release a chemical that get the males going. They will spar for position, and the top male will turn a light, silvery-white color with black trim on the fins. Often they may have pink in the tail and gill area. The top female will do the same, but not so dramatically. The other fish will turn a darker color, indicating submission.
      If you take the male out, the next male in line will change colors and start the breeding process. It’s an interesting thing to watch!

  5. LittleFishy says:

    You actually were able to breed in a 29 gallon tank?? How big where your fish?
    I’m trying it right now, but no success yet.

    • Yes, numerous times. But you’re right, the size of the fish is the key. The fish that have bred in that smaller tank were between 5″ and 9″. We now breed primarily in an 80 gallon tank, and then move the mother to one of our 29 gallon “nurseries” to release her young. We move her on day 10 after breeding, and leave her there for about a week. She then goes back into the breeding tank, and the brood stay in the 29 gallon tank. –Sheri

      • LittleFishy says:

        Wow.. 5″ in a 29 gallon. That sounds very cramped. How many did you put in? 3 female 1 male?

      • We started with 1 male and 2 females, but soon found out how abusive tilapia can be! We ended up with 2 males and 4 females, and still use 2 males and 4-6 females when we start a new breeding colony. It sounds like a lot, but overcrowding the tank tones down the negative behavior. Also, having multiple males and multiple females guarantees you’ll have good breeders. Once in a while you’ll get faulty breeders, like a male that spends more time building nests than mating, or a female that consume her eggs. With multiples, when you identify a faulty breeder you can pull it out & carry on. Everyone has his/her own style, but this has worked very well for us!

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