Backyard Aquaponics
A place to discuss aquaponics

i'm curious how aggressive tilapia are towards each other and other specie of fish when they mature?

if i have some goldfish in the same tank with tilapia, will they get attacked?

tilapia are a chyclid. These fish generally have a strong pecking order, and any fish in with them that is not used to a pecking order tends to get pecked, a lot.
As for tilapia especially, I have no personal experience, but I'd be cautious, especially as the tilapia begin to outsize your goldie.

Even though tilapia are supposedly vegetarians, the truth is they are omnivores, especially when younger, they have a huge protein hunger and will eat any smaller brothers/sisters they can. As for the larger tilapia, they are not likely to attack a smaller fish to eat it but they can be rater violent about that pecking order and especially when it comes to breeding. (most of my tilapia losses have been when I put small numbers of them into breeding tanks.) When there are larger numbers of them in larger tanks, the attention and aggression gets spread out more so stress and death are a bit less likely. I've not actually kept my tilapia directly with any other fish but I think some people have. I would suggest making sure the other fish are tough enough to take care of themselves. Like I expect I could let the catfish and tilapia live in the same tank without the cage separating them if I wanted to but in general it has been easier to keep them separated.

it sounds like it's not recommended to keep tilapias with goldfishes. these videos and their comments agree.

http://www.youtube.com/watch?v=kMKln4lKjyA
http://www.youtube.com/watch?v=iQW5PwUlgXU

Mine have always gotten along fine, but the goldies started at 2" when the tilapia were 1", so perhaps the tilapia started out with some respect. Here are a couple pics. The tilapia are about the same length, but much slimmer (you can see some in the background, same color). The tilapia are far more aggressive toward other tilapia than toward the goldies, catfish, or plecos.

Gee, how many people have goldfish as pets that they actually spend time petting and holding?

I wouldn't go placing adult size tilapia in with equal or slightly smaller fish but if you are putting small tilapia in, just make sure the other fish in there are bigger than the tilapia.

hey i pet my goldfishes all the time as well =] i have no idea if they like it or it's a routine suffocation for them.

hydrophilia - so you don't have any goldfish in the same tank with tilapia that are say twice the size of the gold fish? tilapia are either the same size or smaller, is that true?

Young Tilapia are extremely agressive ,, they happiy eat their brothers ands sisters and would also chew off the arm that feeds them if they could:)
As with near all predators placating is fairly simple ,, a full belly of high protein food.Ever seen those wildlife documentaries where a Gazelle is feeding a few metres from a pride of lions??? Yep the lions must be FULL and more interested in rest than in feeding. This and growth rate are the reasons for feeding young tilapia high protein diet at 4 times a day.
They soon 'learn" their bellies will be filled and loose agression.
Agression period number two comes when they are about 15cm long ,, SEX ,, yes they want to breed , the Males will fight near to death in order to pass their genes to the next generation.This should not be a problem as any serious grower will have male only Tilapia ( and I haven't noted any gay ones).
A full belly , no females around are the ingredients for happy male Tilapia ..... ahh add beer and that may also work for humans,,,LOL ..... joke ladies JOKE.

My tilapia are pretty peaceful. Of course they have alot of room (200 in 1440 gallons). I threw about 15-1.5lb. tilapia together in a 180 gallon tank and so far (2 weeks) they are all fine. Not overly aggressive as far as I can tell. But maybe I'm biased because I've recently been keeping a fahaka pufferfish and I think he should be called a lil faka. Absolute terror that will kill everything and anything.

Smallest goldfish is about 3/4 as long as the largest tilapia in the aquarium, but I may have only females (2) in that tank. The other goldfish are as long as and more massive than any of the 25 tilapia with them.

So far my larger tilapia have left the 2 inch bluegill alone.

I had a female Koi that would come into my hands and I would rub her belly. This I think was a result of me putting my hands in the pool when feeding, she came to me no matter if I fed her or not so I'm not sure of the reason. My Koi would rush to me when I came to feed them, but they were standoffish if it was anyone else. They knew the hand that fed them, this I think was because I always wore bib overalls on the farm and nobody else did. I like to think it was more than conditioned responses but I can't say for sure.