Ive just recently brought API LEAF ZONE fertilizer, I'm just wondering if I should take my carbon filter out because I've heard adding treatments will be taken out because of the carbon filter. Then I'm thinking surely not with plant fertilizer? Please advise. THANKS

I have used all of the plant products on the market at one time or another. Leaf zone, all of the flourish products, Amazon water conditioner, etc. and none have ever mentioned the carbon. My guess is that the plants will suck up most these products before the filter can. It is only my educated guess. My plants do well.
However, just as important as nutrients is lighting. My plants did not thrive until I installed a 200 watt coralife light.

I most be honest I'm not sure about what it will do with a pant treatment but if you ever give your fish med like treatment for ick take out the carbon filter or it will get rid of the mess and it will help your fish little to none.