Aggressive tank mates

HI, I have noticed in my 40breeder where I have a maroon clown and yellow tang only. I have had the clown 9 months now and its been in the 40 for about 5 months. I got a yellow tang about a month ago. The fish is wild caught and arrived in very rough condition. Day 3 it got real bad popeye. The tang is still very finicky but I notice it loves going to where the clown is and just posts up there in an aggressive manner. It will push its tail and bone (weapon) closer but if it gets too close the clown will bite him.

Is this normal dominating behavior or am I gonna wake up to a murder one day.

Any ideas, is this something that will damper down?

It could be a few things…

  1. The most likely is the tank is too small. 40g is very small for any tang, even a kole tang. Tangs are fish that swim long distances every day and being cramped makes them stressed and they’ll act aggressively.

  2. They will defend their “algae patch” pretty aggressively. Does there happen to be a spot it grazes on there? You could try putting nori on the other side, away from the clown.

  3. Tangs are generally unlikely to stop their aggressive behavior unless something changes pretty drastically. (Larger tank, change in fish, etc.)

Thank you for the advise. I have considered those as reasons as well and may very likely be the issue. I will be getting a bigger tank but still planning atm.

I also thought if the fish was not feeling well or sick the aggression would increase. In the tank the tang has about 3 feet to swim down and can circle the tank freely. Now i have seen multiple tangs in small tanks as well as say a ton of fish in a decent sized tank. If one fish has say 30 gallons to swim in and in a bigger tank there may be 100 gallons available but also there are like 3 tangs. Is many fish in one gallon different then 1 fish in 1 gallon? Why can there be a school of tangs in a 400 gallons but it doesn’t work porportionally when reducing tank size or number of fish. At least for me this doesn’t work.

My dream tank I will def have a yellow tang and a purple tang. I’m debating a powder blue. I want a red sea XXL 625 or whatever rated to 133g. Would this be too small for them?

I personally haven’t seen illness cause aggression, it’s possible. Injured fish can act aggressively, but that typical wears off pretty quickly.

It’s more about distance than it is about gallons with what we’re talking about. Tangs typically swim very long distances in the wild (miles a day). 3 feet is not very far for it to swim before having to turn/turn around. Nor is 5’ or 6’ for that matter, but we’ve seen it seems to be “enough.” The general rule of thumb I’ve seen and seen work is nothing under 150g. I have a 30g tank that is 72" x 10" x 10", but I’d still never put a tang in it even though it is technically long enough.

Some fish, like clowns, need smaller tanks because they’re home bodies. They pick a spot and then they don’t stray very far from it. Same with most schooling fish we see in the hobby. They aren’t athletic like tangs, they tend to stay on their reef their whole life.