Hi all, I just ordered a 100 mL box of purigen that comes in a little mesh bag already. It says 100 mL treats 100 US gallons. I have a 20 gallon tank, is it safe to add the whole bag? It looks like it would fit in a whisper cartridge like an ordinary carbon bag. Also, is it ok to not use a carbon bag and just use the purigen, or do I need to use both? Thanks a lot. I'm hoping the purigen will clear up my water a tad and bring the nitrates down a smidge.