When more S beads need to be added, remove the coral chunks that they included with the pkg...it doesn't work in buffering the acidic environment as it's all in the same chamber. Ideally the effluent should go into a second chamber to buffer up the pH like a dual stage Ca-Rx
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Get a tallish open top plastic container and drill a few fine holes in the bottom. Fill with aragonite/crushed coral, coral chunks and hang off the inside of the sump. Have the S-Rx effluent drip into that to buffer up the pH.
HTH