Tilapia, as a rule, are territorial fish and kind of jackasses in a communal setting which can be a fairly big challenge to those looking to establish aquaponics systems.
As an aquaponist, your success will be based in some degree on understanding what is happening in the tank and doing your best to ensure that everything is kept calm and happy.
There is a hierarchy and societal structure for tilapia that is based on aggressiveness, sex, size and hormones.
Male Tilapia will fight other each other to establish dominance, entice females and for territory to set up nests for breeding.
In captivity, these fish will carry over all of the wild instincts but in the confined space we provide can lead to some very big issues.
Nesting in the wild can be very impressive and look like a mine field with hundreds and even thousands of nests with competitive fish standing guard vying for a chance to breed.
In captivity, we attempt to give them a nest (usually in the form of a flower pot or some other structure with a bowl shape) to call territory and allow for breeding to happen.
In both cases, the males will attempt to hold ground and highly contest all of the other fish around them. Any fish that attempts to take the nest or move into the designated breeding area must be driven off or even killed by the fish holding the territory or face the fate itself.
Donna caught some video of the tilapia nesting at the Alberta Aquaponics Tilapia Donation To The Calgary Zoo when we were last there showing how the males create and hold nests. (Sadly it is somewhat hard to see in the hippo waters of the zoo).
On a large scale area in the wild, this can be accommodated to some respect with natural formations for fish to hide in, lots of room to establish nests and to some capacity even predation which cuts down on the numbers of fish as a whole.
It is normal for male tilapia to fight (it looks much like chasing or Sumo) and attempt to toss other fish out of the tank. If they are unable to rid the fish from their defined territory, they will rip the skin off of the other fish or run them until the stress kills them.
Females will also compete in a standard tank. Females attempt to rip the lips off of each other. This, because of them being mouth brooders, means that they are not just killing the female fish by stopping her from eating properly, but also killing any possibility of her blood line carrying on.
When combined you are in for a real shake up when it comes to mating.
Males will attempt to achieve dominance in the tank, beating up all of the other males around them. They will pick the nesting area and start defending it by chasing all males from the area, then attempt to find a female that they can push (read beat up) into the breeding territory.
Females can be killed by the males at this point with the aggression levels they have and efforts in keeping the females in the nest area.
Once the female is in the territory and receptive, she will start cleaning the nest area until she comes into cycle at which time a hormone is released in her urine that draws the male to her to breed. This hormone will also draw in other males in the area adding to the charged environment.
The male will then hyper guard the nest while the female lays eggs. The male will swoop in and milt the eggs, then go off to guard and defend again until the next batch of eggs is laid (read go beat up everything it can come in contact with in the tank).
The female at this point will begin picking up the fertilized eggs in her mouth where she will roll them to oxygenate them by taking little bites of water. The eggs can be seen in her mouth as she rolls them around at this point. She will continue the cycle until she has no more eggs to pick up, while the male continues coming back to milt and then guard. Once she is completed in her duty to drop and pick up eggs the male will then drive her from the nest (read beat her up) so he can find another female to mate with.
At this time the female is vulnerable in the tank from all of the other fish. She will not eat for the next few weeks while she rears her young and will weaken over time. Other fish in the tank (both male and female) will attempt to beat her up and get her to spit her eggs and fry of which they will eat given the opportunity.
In a single confined fish tank, this is a lot to manage, and it is up to the aquaponist to help sort out.
For a good breeding environment, I suggest a few things.
Be able to see your fish. If you are unable to see what is going on in the tank and what your fish are doing it is unlikely that you will be able to help the reproductive process with your fish. Look for signs of territory owning, watch for fish with distended chins or females rolling eggs.
Make sure you have brood tanks available for the incubating females and eggs or better yet, be able to move the non-brooding fish to another communal tank (harder to do usually due to the size needed for the tanks).
Once the female has picked up the eggs, collect her and the eggs (as calmly as possible to stop her from spitting out the eggs) and migrate her to another tank on her own. This will lower the stress levels overall for the mother and allow for the fry to have the best chance of not being eaten. (Ensure that you have a filtration system that will not allow the fry to get sucked into it. Fry have an uncanny ability of finding ways into canister filters, grow beds and swirl filters. <check these daily>)
These tanks should be set up and running with an already active bacterial load so that you are not putting the fish through a full nitrate cycle. You should have a tank for the female to brood out and another tank to move the female to once she has completed looking after the fry to build her weight back up (remember she has not eaten for weeks at this point) before putting her back in the general population tanks.
For many aquaponists, fish breeding seems very daunting and equipment intensive, so the desire to just not have the fish able to reproduce at all seems to be the key. This is far from resolving the issues overall in a tank however. The fish will still become aggressive with one another even if they are not allowed to breed.
There are many schools of thought on how to resolve some of the issues; some advisable and successful, others not so much:
Increase the fish density or use a smaller tank:
(This is something I do not recommend at all.)
In aquaponics which is based on bacterial loads and stability to keep a handle on the nitrate cycle, small water volumes are problematic and very hard to manage. Bigger water volumes and an even stocking density is a key factor in the stability and success of an aquaponics garden. By messing with this, you set yourself up for many potential pitfalls along that way.
For the tilapia, territory is based on the space size they believe they need for a nest and not a factor in the small size of the fish tank. (Equating this to humans, the house size a family requires or desires is not a factor based on the size of township of which they live in) Although you are giving them a physical boundary in which to live, the fish will not take that into account for nest building or territory holding. This can lead to very heavy pressure of other fish and worse.
The thought process of keeping a higher fish densities to cut down on breeding is only somewhat factual and successful.
The higher numbers in the volume of living space creates more pressure in the tank for space which will cut down on the chances of successful breeding but also creates more stress overall which will have a have impact on the health of your fish, their growing abilities and your overall success of the aquaponics system. High levels of stress also open up other problems like diseases as the fish have a lowered immune system decreasing the abilities to fight off infection and viruses meaning that it could cause a cascade effect in losses should something go wrong. The higher concentration also means there is usually a higher competition level for food with the biggest, most dominant and aggressive fish gobbling up offerings quickly and the lesser fish being pushed to the sides creating an overall weakness for problems to arise in.
Sex Segregation or single chromosome exclusion:
Tilapia are hard to sex in the juvenile (fingerling) stage under 4” in length. It is estimated that even professionals who do sexing full time are only able to get it right about 70% of the time at that size and 50% of the time with smaller fish. Sexing fish is also time consuming and stressful on the fish which is something most breeders attempt to avoid at all cost as time equates to money and stressed fish equate to problems.
As a result, most breeders will simply scoop out the fish they have for sale and you will get a mix of both males and female stock. (This is actually a good thing for most people doing aquaponics because, in my opinion, fish breeding and maintaining your own fish stock is as important as seed collection of an aquaponics system for sustainability.)
For many however, the task of fish breeding seems to be a daunting one so they assume that by ridding the tank of one sex or the other it will make the process easier. This is usually not the case. Hormones and instinct are formidable, unseen opponents and regardless of members of the opposite sex being there, standard societal and dominance competition will occur.
Science has created a method of single sexing fish in order to create male only tilapia.
Many states and provinces are actually looking at this for being a means to resolve the invasive species issues for the fish long term in North America and have thought about pushing for a mandate for all potential invasive fish species (tilapia included) to be single sexed.
For this the fish are milked of the eggs which are then put into colder water to incubate. The fish are then subjected to a hormone that modifies the chromosomes of the fish producing a triploid or male only gender.
There are some issues I have with this.
First the eggs that are incubated at the lower temperatures and exposed to the hormone cause huge losses in the viable fish fry. In my mind this is a huge waste and human intervention where it should not be.
Second, I do not want a GMO fish in an aquaponics system when I am attempting to grow the best and healthiest possible food. Take whatever stand on GMO’s you like, When I am distributing fish to the public, I feel that it is my duty and responsibility to give them the best possible stock I can give them, which to me means, non-GMO and organically fed. I can’t change things back the other way if I contaminate it in any form.
Third, the term triploid and male only does not always mean that is what you are getting. It is suggested and documented that as many as 10 – 15% of the fish will be female and could still be potentially viable. You will be paying an extra cost for this process on a local level if it is available. If it is not available locally, you can also count on expenses in shipping and permits to get them if you can at all. The end game is that you could still end up with breeding fish for the extra cost and have actually saved nothing in efforts for the price.
What we have had success with:
Tilapia like a living temperature range between 22c to 30c. Breeding temperature in our tanks is usually around 28c. By dropping the tank temperature to around 24c we have found that they are less likely to be in breeding mode. This is not to say that we have not had a couple of them breed anyway, but the chance of having them breed is a lot less.
The hard part here is temperature stability. Fluctuations of a couple degrees can result in unwanted breeding with the temperature change being the driving factor for putting them “in the mood”. With smaller outdoor tanks this can be somewhat harder to manage and compensate for due to outside temperature movements (larger volume, insulated tanks are more stable as a general rule).
Give both sexes a bunch of territory for them to fold. IE: lots of pipes to hide in and own that are of a variety of shapes and sizes. This will imitate nature allowing for smaller fish to own territory that they will feel safe in and can hide from the abuses of the other males and females in the tank. This will allow the females to hide away from being pushed into breeding situations, lower stress levels in the tank and allow for all of the fish to “own property”.
Lower the fish density
Going against the other schools of thought, you can also attempt to lower the fish density in the tank or use a larger water volume of tank. This is not always great for the aquaponics side because it will also lower the nutrients going to the bacteria and plants however it will drop stress levels in the tank and allow for the fish to be more spread out with less competition.
Let Nature take its course
If you have fish that breed and you don’t want to raise them, leave the female and babies in the tank with the other fish. Chances are that the female will end up being bullied to the point where very few if any of the fish will make it to adulthood. Keep an eye on the female because it is very possible that she may be killed by the other fish attempting to get her eggs.
Some folks will catch the female with the eggs and use a pipette to either suck out or wash the eggs out of her mouth into the main tank to stop the cycle.
I hope that this helps in some of the questions and concerns about tilapia as a whole.
There have been many in our group that have managed to rear and raise tilapia fingerlings to full sized fish in both inside and outdoor aquaponics systems. Do not be shy about asking questions and getting advice on best practices. Remember that we do have a forum on our main website as well as Facebook pages and even a face to face meet up where you can ask questions, offer advice and get involved.