[horteco]

I have a rsm250. It has been up and running for 6 weeks. Finished cycling 2 weeks ago. It went through alot of brown algae followed by even larger amounts of green algae on most of the rocks and all over the glass.

Last week I was given advice from several different sources to add a cuc. Some said just add a few snails. Others suggested a mixture of criters up to 1 per gallon. (65 gal tank). I wanted to start slowly( as everything you read says "START SLOWLY") but against what I read I decided to put in half of the maximum. 12 snails(6 strawberry tophats and 6 trochus) and 20 hermit crabs ( 10 red legged and 10 blue legged). (I got worried about the amount of algae growing. Like a thick unmown lawn)

At first everything went well. I spent about 1.5 hours acclimating them with drips from my tank into the water they came in and included a heater set to 80 degs F. I then carefully placed the cuc in the tank. They immediately went to work. The snails were going thru the algae like they were starved.

The crabs looked like they were getting food as well. The crabs seemed to prefer being on the LR while the snails went everywhere. Each day the algae was being visably reduced. About day three I started to notice My first dead crab. I remembered that they need extra shells in the tank if they are molting, so went out and purchased several differnt sizes of shells. Each day since has seen fewer crabs, while the snails continue to eat the algae (all snails look healthy).

Today one week after adding the cuc there is almost no visable algae, all the snails are still hard at work. All 20 hermit crabs are dead.

Each day the crabs that were alive seemed content working to clean up the tank. The next day the ones that died, were just sitting in there shell not moving, after awhile the body parts (legs and pinchers) would just fall off in the water currents.(this took a day or two after they stopped moving).

I would like to continue to build my tank, I want a coral tank with a few fish, but don't feel thats wise until I figure out what caused the crabs to die.

In hind sight I suspect that there was not enough food in the tank to support the crabs unless they eat algae. But my suspicions are based on little to no knowledge.

If they starved, will my snails be next? as the tank has almost no algae. When the algae is gone do snails need food added. ( I don't have any fish yet so no excess fish food available)

tank conditions are as follows:

Salinity = 1.026
Temp = 81.5 F
pH = 8.1
NH3 = 0.0
NO2 = less than 0.1 or less
NO3 = less than 5.0
Ca = 460
dKH = 9
PO4 = 0.25 or less

Did an 8 gal water change last wednesday.

lights 234 watts ho t5 mixed 12 on 12 off
moon lights on all night

carbon in with pump in back

skimmer not removing much skimmate. some not much.

If anyone has ideas as to whats happening in my tank, I would appreciate your experienced advice.


thanks