One-handed removal of the RAIN2 (or the RAIN4) dome LED lid lets you get to the growth easily. In this photo, the water pipe is turned a bit so the growth is more visible. And now, with one more hand you can lift the tray and all the growth out, or remove the red cap and slide the screen out. Without turning off the water or disconnecting anything else.
Answer to question: Because in saltwater, scrubbers absorb nutrients much faster than chaeto refugiums and thus can be about 5 times smaller; and for freshwater, chaeto does not grow at all (the only other option is plants)
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