Aggressive Rasboras

[Madiiiiiii]

I own four harlequin rasboras and they have recently become more aggressive towards each other. One of them is a bit fatter than before, so my hypothesis is that she has eggs and the others are males fighting over her. However, I really don’t want them to get hurt. Other sources said to feed them live food to get them to calm down but we don’t have any. Does anyone have any suggestions on how to get them to calm down?

 

[Byron]

This is likely normal behaviour, though I would have to observe it to be certain. But shoaling fish (fish that live in groups of their own species) frequently have interactions related to spawning, display, hierarchy, etc.

However, there is one problem here, and that is the number. Most sources suggest a minimum of six, and while this is certainly better than five or four or three, having a few more than six is better for the fish. Rasbora need more than this, and I would suggest at least seven or eight in total. So acquiring three or four more is a very good idea, and you should do this as soon as you can.

Live foods will have no impact whatsoever on shoaling behaviours. It might induce spawning more, but nothing else. The environment itself is important, making sure the water parameters are suitable for the species, and the tank aquascape provides what they may need (cover, not bright overhead light, calm water, non-aggressive tankmates).

 

[Madiiiiiii]

Unfortunately we are unable to get any more rasboras. I think that ours will be fine however. The first four we got three of them died and we had one left alone for a while. He did pretty good alone, he swam around pretty happily and was pretty healthy. After we got these next three (who all were smaller than) he sorta took up a protector role. The fish are content so I think they will be good with just them.

 

[Byron]

Unfortunately we are unable to get any more rasboras. I think that ours will be fine however. The first four we got three of them died and we had one left alone for a while. He did pretty good alone, he swam around pretty happily and was pretty healthy. After we got these next three (who all were smaller than) he sorta took up a protector role. The fish are content so I think they will be good with just them.

The four rasbora will not be as "good" as they would with a few more, but that is not your fault as they are not available. Just so you know; shoaling fish have very specific needs for numbers and they can be affected without.

 

[Moss Ball]

You also need to realise that if you have just 1 female the males will hassle ger to death.
Adding more females will make things better as the males will spread out thier attention.