I apologize if this is a stupid question. I set up a 20 gallon long planted aquarium for my betta. I added 9 pigmy corydoras and a few snails. I recently added Indian Almond leaves, cones, driftwood and I have a nice tint to the water. I want to add RCS. Because I want reduced current for the betta I used an Aquaclear HOB filter suitable for 5 to 20 gallons. The sponge in the filter for mechanical filtration gets black pretty quickly. I was concerned it was too small for the biolodein the tank and was going to upgrade the filter and deal with the increased current, but it dawned upon me the black color may just be from the tannins. Can anyone please let me know if that is the case and how I can tell if the filtration is enough. Thank you in advance.
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