Fish Breathing Hard

Last week (Feb 15) I did my regular 50% water change and I add Excel like I usually do I must have made a dosing error or something because the next morning I lost 5 fish and all the fish were breathing hard at the top of the water column....After I did my share of :swear:...I added an airstone for several hours the fish seemed to get back to normal....so I took the airstone off, but I noticed that at night when the light go off they start breathing hard.

Could the excel level still be high after a couple of days? The only other thing I did different was add some Melafix and moved the powerhead closer to the diy co2 source....I dont think the Melafix had anything to do with it...maybe the co2 is being distrubited better with the power head closer to the reactor?

Okay so I did another weekly water change (Feb 22)... and added the recommend Excel after a large water change...The fish where still breathing hard so yesterday I decided to take the DIY CO2 off...the fish seemed to stop breathing hard...but today when I turned the lights on the fish seem to be breathing hard..I have not lost any other fish I just find it weird that the fish are breathing hard....Any Suggestions?

Water parameters:
pH =6.8
KH = 5
Ammonia = 0
Nitrite = 0
Temp = 78
EI dosing
Excel as recommended

Well my ammonia is 0.....

jpappy789 said:

It's very hard to OD on DIY Co2 as you don't get a whole lot out of it. A drop checker would confirm that though.

Are you using a conditioner?
Tank size and stock?

Click to expand...

I use
Start Right...
It a 60 Gal Tank....