Yeah. Tbh I wouldn't buy anything to eat it. Because that's actually adding to the problem, which is excess phosphates and nitrates from livestock and feeding. Like you said, It's absorbed into the rock. Keep up on your maintenance to pull the phosphate from your rock. Gfo, skimmer, ats, refugium, manual removal, siphoning the dirt out, eliminate dead spots in flow are good things to focus on. How long is your photo period?
Btw I really like your rock scape lol.
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