Vacation - disaster strikes - please help

[JJP161]

I have a 75 gallon tank with 150 lbs live rock and 75 lbs live sand. My tank has been up and running since feb. with everything going great the last couple of months. I had 2 clowns, 2 cardinals, a foxface, a butterfly, 6 line wrasse and a goby. I have a number of soft corals as well, lots of inverts. I returned from vacation to find a very large rock crab plus a baby, a mantis shrimp and a large thing 2-3" oval shaped thing that looks like a flat gray piece of rubber with eyes, I think it is a flatworm? Plus my fish apparently have some ich again. The ich was treated before in a hospital tank when I only had 2 fish and the main tank was without fish for 8 weeks as recommended. The mantis I knew about and have been trying to trap for over a month before my vacation with no success. The corals are doing great, inverts are disappearing quickly and I have 3 fish still alive, 2 cardinals and the foxface. The 2 clowns and the goby completely disappeared with no signs of their remains. Any help would be great. Thank-you

Water
Temp 78
SG 1.024
Ammonia 0
Nitrites 0
Nitrates <10
pH 8.2
Calcium 450
Phosphate 0
Alkalinity 11

[ckusnierek]

Mantis or crab probally got the fish in their sleep and made quick work of them....

As far as the Ich can you get the rest of the fish out and into QT?

How long were you gone? was the tank being cared for?

I had a villian in my tank for a few months and could not catch him nor did I ever see it I thought it was a mantis(clicking noise) after it killed about $250 worth of fish I tried a homade trap...
basically cut the top off a 20oz pop bottle and invert it. throw some mysis, krill or somthing like that in there and chack it in the morning. within in two days I had caught a Xanthid crab. try it I bet if you can see crabs and babies you probally have alot more in there than you think.... especially with that much LR there is tons of places for them to hide....

[JJP161]

I can get the remaining fish into a qt tank later today. Though the ich does seem to be clearing some. I was gone for a week and the tank was cared for. The mantis would it into the trap most likely but the Xanthid crab would never fit through that size opening. He is big, probably 3". I saw Hikari has a product that is supposed to take care of Flatworms but no one can tell me if it is reef safe. Is there a way I can be sure to get out all of these bad critters once and for all?

I've come up with a last resort measure but I really hate to have to go through all of this if there is another way? Plus my rock has a ton of great stuff on it and I hate to lose any of it.

1. get a couple of large trash cans and fill with saltwater
2. Set up hospital tank and move all corals, fish & inverts there
3. Remove rock from diplay tank to trash cans, piece by piece searching for and removing the "bad guys"?
4. Replace all rock to display tank
5. Replace corals and inverts
6. Treat fish in hospital tank for 8 weeks

[crvz]

If you want to kill sessile inverts indiscriminately, you could treat with interceptor (dog worm medicine). It's a bit of overkill, but it would kill all the crabs and shrimp if you did a strong dose, without otherwise hurting coral or fish. There's a lot of history of people using it to kill off redbugs in their tanks, so it's not too crazy.

[Loverotties]

Watch out with your fingers and hands!He can get a good grip of them,