Rummy Nose Tetra With CO2

[jagillham]

My RNT's seem to not be enjoying my CO2 levels, despite the other fish in there being OK.

You'll have to excuse the 1yr old and cat trying to get involved!


(Video link)

The CO2 does not seem particually high, the drop checker is green and I still have melt issues & limited plant growth. I'm dosing EI.

When I turn the CO2 up marginally the RNT stay low, lose colour, and their mouths open / close quickly.

Any ideas what it could be? My water is pretty hard if that makes any difference, I think somewhere between 12-14 when tested before.

 

[Crossocheilus]

Perhaps oxygen levels are on the low side, how much surface movement do you have? If there is no surface movement and unhappy plants there may be very little oxygen. Increaseing surface rippling will increase oxygen but also drive off CO2 so you may need to increase CO2 as well.

I have found that some fish have a lower tolerance for CO2 (e.g. threadfin rainbow fish) so it could just be this.