When I went to school we made gun racks and hunting knifes in shop class. It's to bad our world has degenerated to a level where our children are not safe in their classrooms.
Who's fault is it? What do we do to rectify the problem?
I'm not so sure it's a sponge. I get some growths like that now and then, never that long. My sailfin tang spends his time grazing the rocks, so not much escapes his hungry little mouth. I think it is more likely some kind of macro algae.
I lost a nice big sabae anemone to a Seio 2600 powerhead. I took a piece of that foam prefilter stuff and cut a hole in the center of it and slid it over the intake. I removed it after the new anemone had settled in. If you do cover the intake with some type of foam filter, make sure you clean it the same as you would clean your filter socks.
I thought that Arrow crabs were not reef safe. I have a six line wrasse, it's an interesting fish. But he's taken out my peppermint shrimp. It's fast, really fast very fun to watch.
I left mine clear. the coraline algae has covered most of it. You can still see some of the hardware on the back, towards the top. It's not that big of a deal is it? It's what's inside that counts.
You don't want to leave the glass top on your tank if you're going to run M.H.s. It will cause condensation and reduce the light into your tank.
If you're concerned about critters jumping out, try that plastic egg crate stuff. It's sold at Lowe's and Home depot.
I used a Aqua-C remora pro on a 116 gal tank for 3 or 4 months never had a problem. I think they are one of the best H.O.T. skimmers for the money. IMO