Since I have been having continual problems with nitrite levels despite constant water changes, I am looking into chemical options to get these levels more stable. So far, I have looked at Nitra-Zorb, stesszyme water conditoner, and Chemi-Pure. As far as the filter medias go, I don't know much about them; is it something you just place in your current filter? Also, which product would you recommend (it can be one of the ones above or something else). Thanks!