Use fertilizers that are designed to be used for planted tanks. Seachem flourish or brightwell florin. Miracle grow is great for a garden and has the same chemical compounds with the exception of binders to keep them from clumping that can be detrimental to the phibs. Some ferts clump when mixed in water, like iron and phosphorous when used in dry forms. Best to use something that is proven to be animal safe.
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