Hey,
I have a 29 gallon tank with 3 glass cats, 3 dalmation mollies, 3 swordtails, and 2 guppies. This morning one of my mollies is hanging out near the bottom of the tank, and his fins are clamped. He did swim up to eat.
I did my weekly partial water change Friday. Nitrates are 40, nitrites 0, pH 6.8, temp 78.
What should I do for this molly?
Thanks!

How long has your tank been up and running with fish? Are you sure theres no ammonia? How long have you had the molly? No one is picking on him, are they?

Sorry to hear about your fish!
As Jsrtist suggested you want to make sure that you have 0 ammonia.
A couple of things jumped out at me.....40 nitrates seems a bit high with the amount of fish you have....you might want to do another water change. Also you might want to up your temperature in there to 80º - mollies really do prefer warmer water. Make sure you are feeding your fish spirulina flakes too as mollies do much better with alot of greens in their diet. The last has to do with your pH. Aside from the glass cats, the rest of your fish would rather be in alkaline water with a pH above 7.0. You might want to consider adding buffers to this tank to get the pH up....

HTH

Update--the tank has been up for over a month; I used biospira so it cycled very quickly.
After I posted that post about the molly, the next day that molly and one other were stuck to the filter, but were alive. I got them off with the net, but unfortunately both of them have died. I have never had good luck with mollies for some reason.
Since they were ill, I did up the temp to 80. Need to check the nitrates again. I have also added 6 guppies to the tank. I always lightly salt that tank, but added a little more salt hoping it would help.
Would it be OK to add a buffer to increase the pH and leave the glass cats in there? I put them in that tank for two reasons--I read that they do well in brackish tanks, as do the livebearers, and I could hardly ever see them in the 55 gallon--they always stayed hidden in the back.
thanks!

What is a clamped fin?

It is where they keep their fins close to their body instead of relaxed. This particular molly was a lyretail, and the ends of his tailfin were actually crossing instead of being opened up.

From what I've read, the glass cats will accept a wide pH range so upping the pH in this tank shouldn't hurt them, just remember to do so slowly!!

OK, thanks!

Mollies like brackish water so this is probably why you aren't having much luck with them.

fishyfan, that's why I put them in this tank with the other livebearers, and have been adding salt. Maybe I don't have it salty enough yet. I wanted to increase the salt level gradually so it wouldn't be a shock to any of them.