I have a 20 gallon back up tank / Qt tank that I've been dumping skimmate in for a couple months now that I get from my 75 gallon DT skimmer. I've never changed the water, only added rodi water to top it off. I tested the phosphate and Nitrate today in the backup tank. I was expecting both to be pretty high but phosphate was .06 and Nitrate was 10.6. There's no fish in it. Just copepods, sand and nuisance algae. I'm just a little confused as to how I keep throwing skimmate into a tank with no chemical filtration, just foam and ceramic tiles in a hob filter, yet the phosphate and nitrates are not very high.