Aggressive Glowfish/harassment

I have 5 Glofish (two female and three males) in a 20 long, and there has been a lot of aggression lately. They've been in the tank for several months, and although one male in particular has been aggressive in the past when it comes feeding time (when they see me approach the tank), it has gotten really bad now. I watched them this morning for several minutes and two of the males were harassing one of the females (not sure why they didn't really bother the other female) non-stop to the point of exhaustion. I removed one of the more aggressive males and placed him in a breeding tank temporarily until I can get the issue resolved. The one I removed was the latest addition, and has been the aggressor in the past, but not to this extent. And now the other two males seem to have picked up on his behavior and have been ganging up on one of the females. What should I do? Remove the males and put them in their own tank? Get more females to outnumber the males?

 

You might have to keep the males and females separate. They usually calm down after that. If you want more buy a few more fish and sex them separately. But that behavior pretty common with most schooling fish

 

I think I'll take out the females and put them in my other tetra tank (20 gallon with 6 Glowlight). Except then I'll have three males in one tank and two females in another. Wouldn't I then need to increase their numbers in each respective tank?

It's really bad. Like not just chasing, but constantly swimming right beside the female and flapping against her non-stop. I feel bad and angry at the same time.

 

What kind of glo fish are these?
Do you have any other fish in the 20? I would get some more. Depending on what kind they are I would aI'm for 8-10 total. Gender shouldn't matter too much but 3 or 4 males with 5-6 females would be great.

 

They are the Blackskirt Tetra kind. Okay, so I can add a couple more females and see if that helps. I figured it was a territorial thing, in which case adding more would make things worse. Only one way to find out.

 

They are schooling fish so more is better. They can become aggressive if kept in too small groups. They don't get territorial since they live in very large groups in the wild.

 

I see. My only concern with increasing their numbers is that I have a Dwarf Gourami in that tank as well, so that could be problematic (he can barely get a piece of food as it is). Maybe I should remove the Gourami and put him in the other tank with a more peaceful species.

Would a pair of Bolivian Rams and a single Dwarf Gourami get along in a 20 gallon? Then other 20 gallon would have 10+ Glofish and the 5 Corydora that currently reside there.

 

A dwarf gourami and a bolvian ram should be fine in a 20 gallon.

In a 20 gallon don't do more than 12 glo tetras.

 

One ram, not two though?

 

Two could work but you'd have to keep an eye on them

 

I decreased the water temperature from 78 to 76 recently. Could that be causing some aggression?

 

Two could work but you'd have to keep an eye on them

I ended up purchasing a single Crown Ruby Bolivian Ram. I didn't even know these existed until today. This will be in the 20 gallon along with 6 Glowlights, my Dwarf Gourami, and five peppered Corys.

 

I decreased the water temperature from 78 to 76 recently. Could that be causing some aggression?

Generally warmer water increases aggression. I would lower the temperature to around 73f, since 76f is on the warm side for them.