Backyard Aquaponics

Are big Tilapia Fish aggressive ?
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Author:  DanaPT [ May 5th, '18, 04:24 ]
Post subject:  Are big Tilapia Fish aggressive ?

Since I had the tilapia massacre, I moved the surviving small 4-5 inch fish into the larger tank with the bigger ones that are 10+ inches. there were only 7-10 fish I moved over.

I'm trying to figure out why i've recovered 5 of the small 4-5 inch dead fish over past 2 weeks.

Visibly, they all looked healthy days earlier when video recorded their activity for 10 minutes (from inside the tank). I didn't see any hostilities among the fish but I guess I'll have to study the video more closely.

On inspection of one of the swirl filters, I noticed a White coating on parts of the fittings. IT looked like carpet, a mold of sorts covering the hard particles. I cleaned out that filter and so far no signs of white stuff's return to the filter.

The big fish all appear healthy. Nitrate/ite levels are at 0 ppm according to my API strips. PH looks high at 9.

Plants looking good. MY tomatoes held over from last summer and are already kicking out fruit.

Any ideas would be helpful.

Author:  scotty435 [ May 6th, '18, 14:15 ]
Post subject:  Re: Are big Tilapia Fish aggressive ?

I don't know the answer to your question but if when you look at the dead fish are you seeing anything that looks like wounds? Seems like if the deaths are due to aggression you should see some signs.

Were the deaths before or after you took care of the mold? Any deaths after cleaning the system?

Author:  DanaPT [ May 7th, '18, 05:39 ]
Post subject:  Re: Are big Tilapia Fish aggressive ?


I've uploaded pics of the fish and the white film.

The white film has returned. Since the first clean out I lost the one gold fish.

There are no signs of this in the tanks that I can see. The water is super clear and I can see the bottom.

thanks for any input!

dead gf 1.jpg
dead gf 1.jpg [ 86.28 KiB | Viewed 6546 times ]
dead tilapia 1.jpg
dead tilapia 1.jpg [ 158.27 KiB | Viewed 6546 times ]
File comment: white film
Swirl filter white film.jpg
Swirl filter white film.jpg [ 110.46 KiB | Viewed 6546 times ]

Author:  scotty435 [ May 7th, '18, 14:20 ]
Post subject:  Re: Are big Tilapia Fish aggressive ?

Everything looks normal to me :dontknow: . Stress can kill fish and these have certainly been through a lot. High nitrites in the 50 gallon tank they were in before or wide differences in parameters between the two tanks might kill them as well.

Author:  DanaPT [ May 10th, '18, 01:21 ]
Post subject:  Re: Are big Tilapia Fish aggressive ?

Thank you sir for your opinion.

So far all seems "normal".

Any ideas what that white film is? looks like it's alive (probably is)

Are there bacteria's that are not beneficial to a system?

Author:  scotty435 [ May 10th, '18, 16:36 ]
Post subject:  Re: Are big Tilapia Fish aggressive ?

Really can't tell what the film is or tell for certain which part of the filter you're referring to (I'm thinking it's toward the front of the filter). Sometimes it's easier to see these in person or with some knowledge of what's changed. The film is probably a bio-film made up of living bacteria but it could be some other type of organism or a mix of organisms. Most organisms don't cause problems and I kind of doubt this one is.

DanaPT wrote:
Are there bacteria's that are not beneficial to a system?


If you're thinking that this white mass is causing your fish problems a UV filter inline between the filter and your fish tank could help. I think it's more likely just a shock problem but UV is worth considering.

Author:  William [ May 10th, '18, 23:07 ]
Post subject:  Re: Are big Tilapia Fish aggressive ?

Hi how are you.. How many tilapia fish can i keep in a 1000 L pond?
How much food can i feed them per day?

Author:  rininger85 [ May 11th, '18, 00:38 ]
Post subject:  Re: Are big Tilapia Fish aggressive ?

Adult tilapia are extremely aggressive. The males are only interested in shagging so they will go after other males to try and kill them so they can have all the ladies to themselves and the females don't like that the other females bought the same outfit as them... and if there aren't enough ladies then the guys aren't able to live as vicariously as often as they'd like and they end up hurting the ladies that aren't at the same level as they are... kind of like the Aussie lifestyle from what I'm told =)

Tilapia aggression is somewhat managed by crowding... if there are multiple bullies in the tank then the bullies might keep to themselves a bit more and not battle for territory... but if you are introducing new tilapia to established tilapia you're probably not going to have a lot of luck because the new tilapia are a lot smaller so the bigger bully can push them around more, and the bigger bully has already established the territory as his.

My first breeding group I had 10 full grown tilapia in a 55 gallon tank. I split them in two groups in two different similarly sized tanks and I went from having no aggression to the biggest male in each group killing pretty much everyone including his ladies (apparently they liked the other dude better and weren't putting out for him...)

Author:  DanaPT [ Jun 2nd, '18, 22:47 ]
Post subject:  Re: Are big Tilapia Fish aggressive ?


Wondering if this is a root cause of a fish die off. The count is up to 10 fish dying. After more observation I noticed the smaller fish at the surface breathing the air.

I normally would limit the pumps at night only running for about 1 hr. I learned this phytoplankton uses oxygen at night. By morning DO could be at dangerously low levels.

Now I'll run the system 24 hrs a day in 1 hr cycles.

Hopefully this solves the fish problem. So far this issue is only happening in the 100 gal tank where bigger fish live.

Any feedback would be appreciated.

Author:  rininger85 [ Jun 3rd, '18, 19:57 ]
Post subject:  Re: Are big Tilapia Fish aggressive ?

Unless you are in a remote location where electricity is hard to come by why not run the air 24/7? Air pumps consume relatively low electric to run all the time.

That being said, tilapia don't require a ton of DO like some species do... I've had tilapia in overpopulated dirty tanks with no air or moving water for a couple days before with no issues.

Author:  DanaPT [ Jun 5th, '18, 21:35 ]
Post subject:  Re: Are big Tilapia Fish aggressive ?

Thanks for the reply. The pump I turn off during the night is they cycling of water. I also realized I tinkered with how the water flows from growbeds to the fish tank. This resulted in the fish tank not getting cycled properly, leaving low depleted oxygen levels for the fish during the PM and through the warming days.

So untinkered, and reset pumps to flow a couple of times during night. So far so good.

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