I have had my system up and running for about 2 1/2 years now. I have 2 galvanized stock tanks that I painted with 4 coats of roof coating. The coating is starting to wear off in a few spots on both tanks. So far I haven't had any issues with tilapia dying but the more I research the more I'm getting worried that this may become a problem down the road due to the galvanized coating leaching into the water. Since I have 2 tanks I am planning on eventually swapping the fish around and re-coating both tanks. I am doing just fish and no plants so I'm using mechanical filtration only. I have a swirl tank, a 5 micron sediment filter and a carbon filter. The sediment filter gets changed twice a day (I know, a lot of time and money) and I change the carbon filter about once a week. A few questions, will the carbon filter help as far as filtering the leached metal? Also was it OK for me to use roof coating in the first place? I tried to do my research before I built this setup but there is so much info out there and I only have so much time. As stated earlier I have had no problems with fish dying due to water quality only the occasional ones that commit suicide by jumping which I suppose could be a water issue but I don't think it is. Thanks for your advice.