Two Illnesses

[DCtank]

I have a dwarf cory that is swimming upside down in a corkscrew pattern and a red eye tetra whose eyes just started to bulge. Obviously, something is not right.

My water parameters in my 29 gallon tank are all fine except my nitrates which I discovered were high (80+) a couple weeks ago. I've been changing 10 gallons per day since then but the levels are taking a long time to go down. It's hard to tell, because the colors in the tube have never matched the card, but my guess is I'm finally in the 40 range. (I'm using API's master test kit.)

The other (currently healthy) members of the tank are 3 plates, two other dwarf cores, and 5 other red eye tetras.

Any suggestions as to what medicines -- if any -- I should use? I don't have a quarantine tank. Will the medicines negatively affect my biofilter?

 

[FishingMouse]

If your nitrates are high get them down ASAP. It's okay to do multiple wc in a day, and I would change more than 10 gal at a time. A little more than 50%, test in an hour, and keep doing that until they are below 20 ppm.
I can't really say about meds, but I know for sure that levels like that need to be dealt with much more quickly as they are toxic. Most on here would say no more than 20 ppm if possible.

 

[George9]

It would be best to get your nitrates down to below 20 before doing any meds.

It's possible that the Cory and tetra are showing these signs because of the water quality. The red eye tetra probably has pop eye which will get better with pristine water quality.

The Cory probably has a swim bladder problem and I don't think these types of problems are usually curable.