Tiger Barb Problem

[ckm233]

Tank size: 25 litres
pH: 7.2
ammonia: ?
nitrite: 50
nitrate: 0
kH: 8
gH: 6
tank temp: 24 oC
Water changes: third every 1 to 2 weeks.

Hi, Had 5 tiger barbs and one of them recently died and now another 2 are showing symptoms. THought at first it was a swim bladder problem but now I'm not so sure. Every time I feed them for about 24 hours afterwards two of them are struggling and swimming with their heads down. Before the other one died it would just sit at the top of the water. It didn't look bloated or have any trouble with it's scales or eyes. The 2 that are still alive seem to be fine after about 24 hours. I've tried shelled peas; they seem fine until I feed them again. I've tried not feeding for a few days and then it happens again as soon as I feed them. I've had them for 2 years and have always fed them in the same way and with the same brand of food but since this has happened I've tried different food and soak it before I give it to them. If it was disease wouldn't all of them have it? 2 of them seem fine and no problems at all.

Thanks. Any help much appreciated.

 

[WILDER]

Immediate water change and increase aeration.

How long has the tank been set up.
Do you have any other fish in the tank.

Tiger barbs are active fish and the tanks way to small for them.
They need at least a 15 gallon tank.
Also they shouldn't be kept in less than a group of 6.

Swim bladder can also be caused by bad water quality, unstable temp, poor diet of to many dried foods, injury, birth defect, bacterial infection of the swim bladder, internal parasites.