I coated a diy cement rock with layers of clear acrylic paint. I used the Krylon brand. It has been in my tank for almost 2 years and no problems. I also used the clear acrylic to coat wood with the bark still on so it would not rot. It worked.
Thanks for the input. The Krylon paints and acrylics do seem to have positive results. I will try it on the 10 gallon for a while and then if all looks good i will do the 55 and 75 gallon tanks. thanks again.