[jessimae]

I have 5 harlequin rasboras in my 20g. It's moderately planted but still has a lot of open swimming space. My male is chasing the females around the tank incessantly harassing the heck out of the poor things. They're starting to look stressed and try to hide from him in the plants while he zips around the tank. I'm almost positive he's the only male, he's significantly more slender and brighter, the others are all little plumper with not quit as red coloring.

Sometimes they show breeding behavior, him & one of the wrap around each other under my java fern and they'll shake upside down. But most of the time he's just chasing the others.

I figure adding more might diffuse the aggression, but how many should I aim for? I don't want too many as I'd like to add some other types of small fish down the road. Would 3 more help the situation, giving them a school of 8? I'm also going to rearrange my plants to give more hiding spaces.

Thanks!

eta: I've turned the lights off, that's seemed to help. The male is still acting crazy but the girls look more at ease and are out of hiding. The male shakes next to them and tries to corner them. It's like he's going wild trying to get them to breed, but it's stressing the heck out of the girls. I'm going to the lfs this afternoon and getting 3 more. Would it be best to add males or females? Do I need to rearrange my tank when I introduce them?

 

[lauraleellbp]

What other fish do you have in there?

If it's not overstocked, I'd go for a school of around 10 total, that should help diffuse attentions on any one particular fish.

And lots of plant cover would definitely help, too.

Since this is breeding behavior and not territorial, I don't think re-arranging the tank will help much (unless you just move the plants around to create more hiding spots).

 

[jessimae]

I got 5 more. The rasboras are the only fish in there, the tanks well established and I have an eheim 2215 (for up to 90g) so I should have no problem supporting the bioload. These ones are younger and a little smaller, which is why I got 5, I figured in this case the more the better. I also rearranged my plants to give some better hiding spaces. Fingers crossed!

 

[anastasisariel]

I just added 7 Rasbora's to my 29 which also has 12 Cardinals and some shrimp. The rasboras are crazy compared to cardinals. Some times its a male chasing a female and sometimes its the female chasing him, but I'm thinking its a good thing in my tank as the rasboras are probably 4 females to 3 males.

I'm thinking its because my PH is a point lower than the local fish store's; maybe triggering them to spawn.