Algae in a frag tank. What to do?

[stanleo]

I had a QT setup in fish room but after months of never using it as a QT I decided to turn it into a frag tank. IT is 20 gallons tall and the frags grow quite nicely in it. I added a six line wrasse to handle pests. Of course now that it has been running for a month with a frag light, algae is growing. It is bare bottom and the sides and back are painted black. The frags are just softies I took from the DT attached to rock rubble. The algae is not too bad but I do have to scrub the glass every couple days to be able to see into it. It just has a HOB filter with no skimmer. Filter media is filter pads from the DT's sump. every two weeks I replace 75% of the water with water from the DT.

Should I add a CUC? If so, just snails or could I add some hermits? What kind of CUC is appropriate for a frag tank?

Should I do water changes with fresh salt mix? My DT is low nutrients NO3 is 2ppm and PO4 is .03. I do it with water from the DT because I was still going to put new fish into it for observation before adding them to the DT.

Should I add a HOB skimmer?

 

[Reefer40b]

Astrea Snails

 

[Rickybobby]

I agree snails do awesome work!

 

[pseudorand]

Astrea Snails

...but only if you've NEVER treated with copper when it was a QT. I "cleaned" my fish QT after treating with copper and reused it for an invert/frag QT. My frags are actually doing quite well, but 5 of 6 astrea snails died within a few days (kept falling off glass), an emerald crab died within 3 weeks, and some subset of the 10 tiny hermits have died (they're to small to get a good count). After testing everything I could think of thoroughly and posting on R2R, I concluded that residual copper was likely the culprit and the astrea snails must be particularly sensitive to it.

I also learned that there's no home test kit that can test copper at the PPB level necessary to detect toxicity for some marine inverts. I have the Hanna LR checker, but after running multiple tests I got 0 ppb sometimes and 200+ others. I finally contacted Hanna support and they told me the LR tester hasn't been evaluated for seawater use (though heck if I could find that in the manual or product page).

Strangely, I have 1 astrea snail still in the tank that's doing great. Looks like he's got a limpet or something on his shell. Perhaps he's some other similar species that's not as sensitive or something.

 

[Reefer40b]

As long as that rock wasn't used with the copper then you shouldn't have any problems with keeping inverts... even in a tank with copper before.

 

[pseudorand]

As long as that rock wasn't used with the copper then you shouldn't have any problems with keeping inverts... even in a tank with copper before.

My QT was bare bottom and I removed all the decorations. Someone replied to my thread that copper leaches into the silicone in the seems and perhaps also the plastic of the filter (not filter media, which I did not reuse, but the HOB filter itself). I can't prove that having used copper is what killed my inverts, but it's the thing that fits the best. Again, only some inverts will be sensitive to Cu at such untestably low levels, but based on my experience I suspect astrea snails are in that category. Maybe buy one or two to start and add more if they make it.