One of my standard emerald corys got a white growth on his side and tail fin...again! I treated the (75 gallon) tank (73 degrees, only inhabitants are 20 corys, Aquaclear 110 power filter) with Pimafix for a week a couple of weeks ago and he looked cured within the first 72 hours of treatment but ...

I read corys are from small shallow streams in Brazil where the average temperature is 26C / 79F. I also read they like tank set ups that are way cooler - below 74F. So:

What temperature do you keep your corys at (and how are they doing)?

That looks like a good porous sponge. I often rinsed the sponge that burnt out my motor but it was just too fine of a sponge so it exhausted that motor anyway. I will look into the sponge block. Thanks Darrel

I appreciate this excellent feedback! I have a 75 gallon tank with an Aquaclear 110 filter. 17 of my 20 cories are little juveniles. I hesitate to attach a sponge to the intake pipe on my filter to protect it from taking in sand because that burnt out an Aquaclear filter motor on me last year ...

I am currently setting up a second tank for a family of Geophagus Iporangensis (cichlids). Geophagus means "earth eater" because they sift sand when they feed. Consequently, I for sure have to provide them with a sand substrate for this. 3 years of raising cories I had no idea they are also Earth ...

I'm setting up my first serious cories only tank - 11 juvenile emerald cories plus 9 laser orange cories; 75 gallons. If somebody can provide feedback for us on the following 5 substrate questions, that would be excellent and much appreciated:

1- Is it true that gravel substrate erodes cory ...