Losing tetras

[Country joe]

From your tank photo, I am wondering if you have enough surface agitation to exchange gases in/out of the water. In order to get more oxygen in the water, I would put an airstone in the tank too.

I have a 200 litre tank with a fluval 307 and a fluval mini filter, so I don't think I need an air stone.

 

[Fishfunn]

I have a 200 litre tank with a fluval 307 and a fluval mini filter, so I don't think I need an air stone.

Okay, if you have air bubbles from the mini filter or adequate surface agitation. I can't tell by your photo. Also, adding medication to a tank can be an oxygen reducer. Fish going to surface can indicate oxygen issues or other things.

 

[Country joe]

Okay, if you have air bubbles from the mini filter or adequate surface agitation. I can't tell by your photo. Also, adding medication to a tank can be an oxygen reducer. Fish going to surface can indicate oxygen issues or other things.

Thanks, I will move the output up nearer the tank surface, same with the mini filter.