Death of Inverts in Reef Tank

[Tanatous]

Hi All, hoping someone can help me out. I have an established reef tank (up for over two years) that I have a number of fish, coral and inverts in. I had an arrow crab in tank and peppermint shrimp alive and well for at least 9 months of that time (post tank cycling) but recently ANY invert (crab or shrimp) I put in doesn't last more than a month or two. Have had two arrow crabs, one cleaner shrimp and one peppermint shrimp die over the course of the last several months. Fish in tank include Blue Hippo and yellow eye tangs, Bangai Cardinalfish (x4), original damsels from the cycle, one clown, 6 line and Melanurus Wrasse. The tank parameters have been stable with Nitrates below 5ppm (I was showing 0 nitrates for a couple of months but backed off carbon dosing volume), Mag 1350, Calcium 420... only slight issue was an elevated alkalinity at 11 due to a test kit issue (have slowly dropped it down to 9.5. Since the fish are all healthy and the coral are fine what could be killing off the inverts? is it possible one of the fish is picking them off? (on live aquaria in doesn't appear that any would be prone to attacking the inverts). Any help is appreciated.

 

[vetteguy53081]

Alk spike will Always cause problems and quickly.
First to consider: Any changes in LIGHTING, Flow or type of water and of course alk

-What is salinity?
-Are there any foreign bugs such as red bugs, black bugs, Nudibranch or flatworms?? I find reading glasses magnify your viewing for bugs
_ are your test kits accurate?? Taking a water sample to a trusted LFS may spring up surprises with their results

 

[Tanatous]

Salinity is 1.026 hasn't really moved - have large ATO that handles it and water changes I'm very careful with. I haven't seen any bugs other than spaghetti worms (I think I have too many) and lots of asterina stars. I've had my LFS test and even had the mobile aquarium guys that come out periodically test a couple of weeks ago... everything lined up with my test kits. Lighting is the same as it has been no changes there, and no new powerheads etc added. I'm at a loss what could be happening besides the alkalinity increase. I'm assuming an alkalinity of 9.5 wouldn't kill off inverts.

 

[Coralreefer1]

Arrow crabs are very territorial and will not tolerate other Arrow Crabs in the same tank. They can potentially prey on small fish, shrimp, polychaete worms and other inverts as well as coral polyps.
It is possible that that is what happened...Arrow crab might have eaten other inverts.

 

[absowry]

Have you tested for copper? I wouldn't think the corals would tolerate any copper but that's usually first suspect for a total wipe of inverts.

The other thing you might check is iodine (iodide) levels. This helps inverts in the molting process. If your inverts last a month or two but then die suddenly, they might be dying during the molting process.

 

[Tanatous]

I haven't tested for copper - I would assume it would kill the corals as well if there was any copper present? I'll order a test kit for it to be safe however. I haven't done anything with iodide so maybe that is the culprit? With the carbon dosing water changes are much less frequent then when i was first starting the tank as the nitrate stays low for much longer. Is there a standard dosing routine for iodide to keep inverts happy? I have a test kit but it's one of the most difficult to read in my opinion so haven't tested more than a couple of times.