Fish All Just Below Surface

[inq]

Today all of my fish are swimming nose up at the surface of the water

Ammonia 0
Nitrites 0
Nitrates 20
Temp 28

120 l tank that has been set up for 6 months with no problems, no new fish added in last month.

I changed 20% of the water and they all seemed happy for an hour or two but now they've gone back to the top

Last week I was away and came back to find a lot of blue-green algae in tank - I hoovered this off and did a 40% water change. Yesterday some of the fish looked a bit ragged - like fin rot - so added fin rot liquid.

I've turned the temperature down to 26 to see if that helps - any more suggestions?

 

[xxBarneyxx]

Normally if fish are sitting at the surface it is due to poor oxygen content in the water. Doing a water change will increase the oxygen content in the short term but will not fix things for long. Lower the temp to 26° should help. 28 is probably to hot for a lot of fish and the hotter the water then the less oxygen it can contain.

Try to increase the surface movement on the tank to increase the gas exchange between the water and the air. Using an air stone or putting the filter outlet just below the water should do the trick.

 

[gowing238]

I had that problem last week. A 25% water change and airstone soon sorted it out. (echo)! whats your tank size and what stock do you have?

 

[Wendy-Jane]

As xxBarneyXX said, that's usually a sign of a shortage of oxygen. I don't know the specific medication you used for fin rot, but a lot of meds say on them that they reduce the oxygen content of the water, so you need to increase the oxygen/air supply into the tank. If I were you, I'd turn your airflow up, or leave it on full time if you don't already, while you have the fin rot stuff in the tank

 

[greatfish123]

You could also lower the water level a bit and that way the water from the filter will provide further agitation and your tank will receive more oxygen. Like the others said, lower your temp by about 2C.