Sick fish!

Question
Hi,
We have a large pleco that seems to be continually getting skinnier and skinnier.  There are some convicts in the tank that are scratching, too.  We recently did a parasite treatment and we have not seen him scratch since then, but who knows what it is.  Do you have any info. on the shrinking pleco.  He looks very old and about a foot long.  He's huge.  We also have an African tank.  We have a Cobalt blue start acting funny.  At first we thought it was mouth brooding because it's mouth looked full, then after about a week it died.  There was a big white thing in it's mouth.  What in the world might that be?  We didn't look that closely, but we are still having problems in that tank.  Just lost a venustus.  Have a peacock that was sick but seem to be getting better.  It just wouldn't eat for over a week, but started eating again slowly.  Anyway, sorry for all of the questions, but if you have recommendations to any or all of them, let us know!

With much appreciation,
Melissa

Answer
Hello,

When many fish become sick all at once like this, there is usually a common cause for the sickness. There are two main things I recommend you check. First, check the water chemistry. This involves ammonia, nitrites, nitrates and even chlorine. All those are substances that can kill your fish. Another thing to check is that the temperature in the tank is not flucuating, especially if where you live is as cold as where I am right now! Fluctuating temperature can cause the loss of fishes's slime coats, which are used to ward off infection.

If your fish appears itchy then he just might be. Inspect his body closely for parasite. If you see any, treat immediately. As for the lump in the mouth, it could have been a cyst, ulcer or even a tumour. It is hard to say. It may even have been a fungus.

In order to aid the sickly or recovering fish in your tank, I recommend treating the tank with aquarium salt. Follow the instructions of the box carefully as an overdose of salt in a freshwater aquarium is not a good thing. Aquarium salt helps fish to heal, and helps protect their slime coats.

I hope this helps.

Regards,
Stephanie