I have a good bit of past experience with water clarifiers. Acurel is the only one I've ever seen work and it's very reliable ime. Don't have personal experience with plant soil substrate but I've seen planted tank people say Acurel worked for them. Water clarifiers can cause temporary elevated breathing in fish, similar to Melafix. It may vary somewhat with dosage, but is relatively mild, and doesn't last long or damage fish, even when used regularly as I used to do (as in every water change, something I used to do to deal with silt in my well water, now I just have better mechanical filtration).
Besides a diatom filter, a HOT Magnum with a micron cartridge works ime, though you might have to rinse the cartridge a few times as it clogs up (or may even have to change it eventually). I have a HOT Magnum I've had many years, but doesn't do you much good, considering I'm a few hours away from you. But, by now maybe you've got it squared away anyway...?
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