Kinger

I have now lost two dwarf gouramis, and am worried about the rest. The first two were lying on the bottom of the tank, not eating and very lethargic. I have four other gouramis, who appear to have what looks like a grayish, black marking starting near their gills and going down to their bottoms.
None of my other fish, including platys, neon and rummy nose tetras, as well as rainbows and guppys seem to be bothered in the least by whatever is infecting the gouramis.
Nitrate, nitrite, and ammo levels are all normal. PH is somewhat high.
I have also done regular 20 % water changes since I got this tank up and running.
Advice would be appreciated.

sirdarksol

Do any of them look like they have holes or dents in their heads?
This sounds like it might be lateral line erosion.
Poor water quality and poor nutrition seem to be the most common causes.
Check your nitrates and make sure they are 10ppm or lower. If they aren't, do water changes to get them down to that point and maintain them there or lower.

However, I would bet that, since most fish food is of pretty low quality, nutrition is more of the problem here. If you're using the standard Tetra flakes, or other "generic" fish foods, I suggest you try to get your hands on OmegaOne flakes and ditch the Tetra stuff. Pretty much every food other than OmegaOne uses fish meal. OmegaOne uses whole fish, which provides better nutrition. In addition, try to get your hands on Vitachem, which will further help with nutrition. Bloodworms, krill, anything with spirulina, and little bits of fresh veggies will also help.

Welcome to Fishlore and good luck to you and your fish.
Let us know how things are going and ask any questions you come up with.

Kinger

Water quality is fine, however I have been using the standard tetra flakes. Have just switched over to a higher quality food.
What I cannot figure out is why only the gouramis. Everything I have ever heard about them tells me they are tough little dudes.
Thanks

sirdarksol

Gouramis are actually pretty tender. My gourami died of ammonia poisoning before any of the other fish even showed symptoms. I had glassfish, the most delicate fish I care for now, in that tank, and they didn't even have damaged gills by that point.

What is the exact ppm of your water? A lot of test kits list 20+ppm as "okay" when it really isn't.

COBettaCouple

Welcome to Fishlore.

I'd recommend treating your tank water with Prime and adding an air stone if you don't have one. If you can add Vita-Chem or Fish Protector, that would be good too. If you have more than 0 for ammonia or nitrites that is likely the cause, but they may be suffering from internal parasites. 25% water changes daily would be good and I'd see if they'd eat thawed, frozen bloodworms.