Crustaceans dieing - HELP!
 

My crustaceans - 1 cleaner shrimp, 1 peppermint shrimp, 4-5 hermit crabs, and as of today, 2 hitch hiker crabs in my live rock are methodically kicking the bucket. Any ideas of what might be amiss?

Tank specs are: 20 gallon long (30"x12"x14"), new set-up (~3.5 weeks old), approx. 30 lbs of live rock.

Equipment: AC 70, Rio Nano skimmer, Seio 620 powerhead, 30" 36 watt coralife double linear T5 (10,000k & actinic), and 24" 48 watt Nova Extreme T5 high output (10,000k & actinic) lights.

Fish: 2 percula clowns, 1 purple firefish, 1 royal gramma, 1 catalina goby & 1 mandarin dragonet (eats frozen).

Other: 6 snails, 1 torch coral, 1 waving hand xenia, 1 fox coral, chunk of star polyp, medium sized rock covered with green hairy mushrooms, other mushrooms, 1 AWOL (though alive) anemone & 2 feather duster worms.

Chemistry: NH3/NH4 - 0, NO2 - 0, NO3 - 15-20, pH - 8.4/8.5, PO4 - 0, temp - 77.2 F.

Have been doing 10% water changes about twice a week, trying to bring down the nitrates. Also, adding ~15 drops of Aragamilk (calcium & buffer) on a daily basis, along with 2 ml. Reef Solution (minerals, trace elements & vitamins).

Everything is thriving - except the crustaceans; mushrooms are growing and spreading, xenia has grown considerably, torch coral & fox coral look great, star polyps are spreading, fish are active, eating well and have excellent colour.

Sorry about the long post, but hopefully everything necessary is listed.
...Any ideas??? :sad:

Copper get in there somehow? Any brass fittings?

nope, and nope... :neutral: thanks for the suggestions...

High Phosphates???:question:
your water can test ok, but your rock can store high phosphate counts

Hows your salinity?

salinity - 1.022 ...knew I'd forget something....

How could I test to get an acurate reading if such is the case?

I know PO4 will give you a great algae garden, not sure it's ever been reported to kill inverts.

hmmm......did this tank come this way and was setup somewhere else and ran for xx months and you have only had it at your house 3.5 weeks? or was it just setup that fast?

Have you checked the expiry on your test kits?

Are you running any kind of chemical or mechanical media? (like carbon, filter floss, etc.)

I keep my salinity at 1.025---->I agree with Michika (missed that!)

Maybe you could get some kind of nirate sponge to soak it up (nitrate) until you find the source of what is causing it. It is possible it could be overfeeding, could be nitrate/phos stuck in the LR itself, could be in the sandbed.

On the other hand it could be you have an invert predator you don't know about? Perhaps a trapdoor snail (found one of those in my tank last night trying to eat my snail! >:( or a hidden crab could be the culprit....

SG of 1.022 is probably what is doing it. Inverts need a SG of 1.024-1.026.

Was set up that fast; used live sand from established coral tanks from the LFS, and dumped tons of "Special Blend" to cycle the tank.
Have used a couple of test kits; I'm getting the same readings from them all.

Nitrates were low to start with, therefore I suspect I'm responsible for the rise by trying to make sure the mandarine dragonet is getting his fair share. :redface:

Trapdoor snail and/or crab... Hmmm.... Would they leave the bodies lying around?

I started with 1.017 since an LFS "calibrated" my hydrometer after having told me it was out to lunch. I have since figured out it was actually bang on, so I've been increasing the salinity over the past week and a half. Would the lower salinity have had a cumulative effect, since it's only the last 3-4 days that I've been having these issues, and the stow-aways have lived through everything (tank cycle 'n all) 'til now?

...Not trying to be difficult, just trying to figure this out. Thanks for all the input! Any other thoughts?

I would say the combination of low salinity and then the steady increase may have had something to do with it. Inverts, especially crabs and shrimp are hugely sensitive to salinity changes.

Whats "special blend"?

It's bacteria. Very nasty stuff - smells like raw sewage! :shocked!: Seems to work, though.

Thanks for all the suggestions. Guess I'll just chalk it up to the salinity, and keep my fingers crossed that whatever's left will be fine.

How about the possibility of them having starved? New tank, chemistry is well within the acceptable range, everything's growing and doing well - other than a few crustaceans... What's left of the hermit crabs all appear to be thriving now; but then I've also started feeding them directly. They're all ravenous.

my hermits are the same . have you tried pumps off for feeding? if you let some thawed food settle to the bottom they will find shortly. I have recently come to discover that my hermit crabs and blood shrimp really like scavenging for "new life spectrum marine fish formula" 1mm sinking pellet. my hermits have recentlly started to kill my margrita snails for their shells. apparently the 15 i put in there for them wasnt good enough.

There's pretty much no chance they starved seeing as they're all scavengers/opportunistic feeders. Even if you aren't feeding the tank (which you are) they'd still have access to food from the sand and rocks. It's much more likely your tank chemistry isn't as stable as you believe since the tank is less than a month old.