Gasping tetras

[Kevin1962]

Hello all.
I put my fish (18 tetras, lemon and red phantoms. 1 dwarf puffer, 2 yoyos, 2 platties and a guppy) into a 10 gallon (with display tank water) overnight so I could empty and put flourite sand in the 120 display tank.
Tank has completed cycle over 2 weeks ago.
Fish seemed happy in the 10 gallon as I filled it with plants and hiding spots.
This morning, I drip acclimated to the new tank water, matched temps and put them in. The tetras are going a bit squirrely, with heavy breathing.
I had put 2" of water above the new sand, Prime to 150% of the tank volume, filled the tank, turned the filter on and let it settle over night.
My first reaction on seeing the tetras gasping was to dose with Prime again in case my method at filling was faulty.
Could the gasping be stress from the 2 nettings?
Parameters are 0 ammonia, 0 nitrites and <5 nitrates. Temp is 80.7F, pH 7.8
Any warning of recognized problems I'm not aware of is welcome.
The DP is happy as a clam, btw, as are the loaches. She's usually the first to object to conditions and the platties are fine.

 

[Heron]

Gasping fish usually mean a lack of oxygen in the water. Do you have plenty of aeration? Is the temp higher than usual? Higher temps mean less oxygen.

 

[Kevin1962]

I run an fx6 with lots of surface disturbance as well as an internal filter at the other end. I did raise the temp to 81f when I saw what I thought was a spot of ich on a tetra.
I'll lower to 79 and see if that improves their rapid breathing.
Thanks for the response!

 

[Heron]

Is your internal filter air driven or pump driven? If it's not air driven I would recommend adding an airstone to the tank. Lowering the temp should increase the oxygen capacity of the water a bit.
if the problems continue you can get an oxygen test kit for a few quid to see if it's too low.

 

[Kevin1962]

One is powerhead driven, one is San air powered sponge filter.
Most gas exchange occurs at the surface, which area is increased with agitation.
I was worried I was going to start losing fish, so slowly ran 10 gallons of 72f water into the tank. All of the fish congregated on the bottom for the increased O2 and have returned to normal behaviour.
Thank you for the great advice!