At some point you'll probably need extra fertilizer, your fish can supply some but depending on your plant load, light and C02 you may need extra. Liquid ferts are fine, I recommend dry ferts. They are cheaper and last a long time. There are several guys on here that sell them and there are some websites like greenleafaquariums that have every fert you need. I recommend buying each fert individually you'll have more control over what goes in the tank. Here's a list of what I have to give you an idea of what you may need: Plantex B (micro's), KN03, K2S04, KH2S04 (macro's), MGS04, CAS04 (GH booster), and FE chelated 11%. All these cost me around $35. Again you may not need all of these depending on your fish load and water source.
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