Help bully fish

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Elle

Aquarium Advice Apprentice
Joined
Feb 19, 2019
Messages
18
Hello,

I am new to having an aquarium and need advice. I have a 65 gallon tank with three fancy goldfish, one other type of goldfish (can’t remember the specific type but has a normal tail) and one rainbow shark.

I was told at petsmart that the rainbow shark is really an algae eater and is not aggressive like it’s look-alike, the red finned shark. The fish have all been together for about two weeks with no issues. However, the past couple days the rainbow shark has been head butting and chasing one of the fancy goldfish (black moore). He ignores the others. Around the same time, we had some sort of bacterial infection get in the tank. Petsmart said our black moore had fin rot on the top dorsal fin and one of the other fancies had an ulcer. We have since been treating the water (about 3-4 days). The black moore’s fin seemed to be getting better but then I noticed the rainbow shark chasing her again and her fin is back to looking shredded, so I think it may be him doing it.

Why is the rainbow shark only picking on one fish? How can I stop him?
 
PetSmart employees strike again!!!

They lied to you. The rainbow shark and red fin shark are the same thing. They also sold you a tropical fish (rainbow) with a coldwater fish (goldfish). You don't mix the two. They don't have the same water temperature requirements.

Rainbows are aggressive. Ive owned two and they were very territorial. My suggestion is to remove the rainbow because it doesn't belong in a tank with goldfish. You will stress your goldfish to the point of disease and death with higher water temps to accommodate the rainbow and by the sounds of it, the rainbow will stress out and kill the goldfish by it's behavior.
 
Yikes had no idea. I was told he can do well in cold temps so we didn’t put a heater with the tank. I have not had a chance to test the water temp but would guess it is 70-73 range. He is an active swimmer, so it doesn’t appear to be affecting him if it is too cold (unless it’s causing the aggression).

Would adding more caves help? He currently has a cave and there is other short tunnel-like decor, but maybe he needs more places to dwell instead of out in the open with the goldfish?

I have another, smaller tank with tropical fish. It is 13 gallons with one gourami, two Dalmatian mollies, and two Mickey Mouse platties. They are all very happy and active. Would he work better in that tank or are they too timid?
 
I think the consensus is that rainbows should be kept in a minimum tank temp of 75
degrees. He is a tropical fish.

Your current tank temp is probably at the highest end for goldfish at 73 degrees. Ideally 68-70 would be the range.

I guess you could keep your tank at a steady 73 degrees and be okay. But doing so could stress both the rainbow and the goldfish. This will be your decision though. The main issue at the moment is your rainbow is aggressive and is fin nipping your GF. It's only a matter of time before your GF develops disease either from being harassed or injured. That's why I say it would be a good idea to remove him.

The rainbow is way to big for a 13 gallon tank. He needs a minimum of a 4 foot tank. Not only that, but if he's harassing a GF in a 65g tank you can imagine what he'd do to your fish in a 13g.

You could try adding a line of sight break with wood, rocks, or decorations but you'll be experimenting and it could or couldn't work. GF are peaceful and fairly slow moving fish and your rainbow is the opposite.
 
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