Help solve a murder!!

[boomer 453]

The Victim-a sand sifting starfish that had his legs slowly eaten off him over a period of 3 days.
The list of suspects-
1 3" Yellow tang-appears to be easy going
1 Yellow tail Damsel-A shifty looking fish if there ever was one but has never shown much aggressiveness
1 Tomato clown
15 blue leg hermits about 1/4" long

WHODUNNIT?

 

[Anonymous]

1. Do you have a harlequin shrimp in there? They eat only echinoderm feets.

2. In the course of 3 days if something is predating a starfish, you would have a good chance of observing it. Since you're posting here, you obviously haven't. But have you noticed any animal paying particular attention to the star, or following it or hanging around?

3. Last water change: when, tested for what, and what were the readings

 

[Mihai]

Cool off Hwarang, start with the assumption of innocence

It might be for three days, but only for 5 minutes at a time at 2am in the morning.

It's true that we need more details: define "slowly eaten"

M.

 

[Baianotang]

I vote for the tang or hermits.

 

[Baianotang]

Tangs are ever hungry animals its hard to keep up...

 

[Anonymous]

What species of starfish ?
How long have you had it ?
How did you acclimate it ?
Depending on the answers to this, we can then go on to predation.

Regards,
David Mohr

 

[boomer 453]

The particulars-
a sand sifting star that came in a "clean up kit". Also included a red sea star, a couple turbo's and another small star (white with brown stripes-forgot the name)
All have been in the tank about 2 months and were acclimated over a period of 2 hours by adding one ounce of water to each bag every 15 minutes and repeating when the volume of water had doubled.

I never saw anyone harassing or paying particular attention to him-just noticed that the ends of his arms were being eaten. When i first noticed it, i moved him under some rock to give him some protection but the next morning he would be out in the open with more of his arms gone. After 3 days i removed him. I have no shrimp at all, only the fish listed and a firefish

 

[Anonymous]

Ok we'll just call it an Astropecten sp.
Since you've had them a couple of months it wouldn't have been the acclimation.
How long has the tank been set up ?
Someone else asked about water params, by any chance detectable Nitrates ?
What's the salinity ?

Regards,
David Mohr

 

[boomer 453]

Yes, Nitrates are high- 40ppm. Since the top off water supply tests at 5-10ppm im assuming it is coming from the wet/dry.
Salinity is at 1.021
ammonia 0
Nitrite 0
The only chemicals in the tank are carbon and phos-zorb
The tank has been up and running for almost 4 years at this house and was run as a fowlr set-up for 2 years at our previous house.

Switching back to a FOWLR tank over the next few months in an effort to do away with the wet/dry.

 

[Anonymous]

Starfish are extremely sensitive to Nitrates and salinity should be kept close to that of natural sea water 1.025 - 1.026. I believe that none of your critters murdered your starfish it simply couldn't survive in that environment. Now it's possible that a critter ( hermit crab ) may be consuming dead parts though.

Regards,
David Mohr

 

[Eryl Flynn]

Am I hearing you right, you have nitrates in your topoff and change water? If so that is a big problem. If not the nitrates are high, slowly remove the bio balls and add live rock rubble. That should help a bit.

 

[boomer 453]

The top off and change water tests at 5-10ppm nitrate. Since the tank is running at 40-50ppm i have to assume that the wet/dry is the problem. I've started to add live rock and switch to a sand bed as opposed to the crushed coral substrate that is in there now. Added 10# of fiji LR and 15# of oolitic sand so far and will add a little more each month until i end up with 70# of LR and a full sand bed in the tank. Then i'll do away with the wet dry and convert it to a LR/sand sump.

 

[Anonymous]

Colonel Mustard did it with the lead pipe in the ball room!

 

[Eryl Flynn]

That is a start, live rock breaks down nitrates but if you use bio balls with it, they produce nitrates that will not get to the bacteria as quick and easy as if it was produced from the live rock.

The crushed coral can be a problem also, it lets detrius since and bacteria converts to nitrate just like bio balls.

Lastly ditch your water source, you really need to have 0 nitrates in the top off water. Do you use RO water or tap?

 

[boomer 453]

tap right now with plans for an RO/DI sometime in the next 8 weeks or so.
I want to make sure that i have enough live rock in the tank before i remove the bio balls thats why im doing it slowly, i figure once i have 30-40# of LR i should be able to start removing the bio balls

 

[fishinchick]

Sand Sifting starfish have to be one of the worst animals to put in your tank. You have to have a fairly large active sandbed in a very large tank to sufficently feed one sand sifting starfish or they starve to death. I have seen them starve to death in a 100 gallon tank with a DSB that had once been fairly populated with worms (the sand sifters saw to that being cleaned out fast).
When sand sifters die (easily and often since they are very sensitive to shipping, PH/salinity/ammonia/stale hamburgers and everything else you can think of) they desentigrate starting with the legs most often. Literally crumbling before your eyes. I have seen alot of them in my time and they don't do too well on the whole.

There are much better starfish to have in your tank than sand sifting stars. If you want something digging in your sand try nassarius or bumble bee snails instead.