What eats diatom films off sand surface?

[RobertK]

Hi Ron,
I've been fighting a diatom bloom on my sand bed for 4-5 months now. It started on my old sandbed which had too much large CC in it, and it persists on my new 4" ESV oolitic sandbed which I installed 2 months ago. The trocus snails keep the glass and rocks clean but mostly stay off the sandbed. The Nassarius and bristleworms cruise the sand but don't touch the diatoms. I bought some cerith snails but most of them died. I also got some Strombus maculatus from IPSF but they don't cruise the sand either. I added a brown and white Caribbean cuke last week but it eviscerated its guts and I haven't seen it for a few days (I removed the evisceration and everything else in the tank seems fine). The tank is 60 gallons (48 x 15" footprint) and the rocks take up about 1/2 - 2/3 of the floor space, so I don't think there's enough room for a queen conch. I use RO/DI water and have gotten the PO4 and Si levels in the tank down to undetectable levels. NO3 is around 30. Is there anything else I can add that will eat the diatoms off the sand? Should I add another cuke (which type?) or give the eviscerated one some more time to emerge and start eating?
Thanks a million,
Robert

[Edited by RobertK on 01-25-2001 at 10:39 AM]

[rshimek]

Hi Robert,

Well, this is a bit of a quandry. The best animal for your situation would be a queen conch, but I suspect you are dead on with your estimation of having insufficient space for it.

Ceriths sometimes work, but the most common ceriths in the hobby are intertidal, and generally die before long in our systems.

I would suggest another mopping cuke and perhaps the cultivation of some macroalgae to help utilize the essential nutrients will help.

You might also consider getting some spaghetti worms and or other detritus/herbivorous worms (these come in the detritivore kits).

Really the best long term herbivores are the small flatworms (not the red one!) and bristle worms that develop in the sand bed as it matures. Personally, if this were my tank, I would do everything I could to boost the sand bed diversity, and try to get some macroalgae growing some where in the system.

[RobertK]

Thanks, Ron.
I was thinking of adding some more spaghetti worms. I did seed the ESV sand with kits from IPSF and IA as well as some of the sand from my old system (probably a mistake in retrospect since I seem to have imported the algae bloom with it) but I am not seeing as many worm burrows through the glass as I would expect after two months. One of these days I'll get around to doing a microscopic exam and critter count but I'm sure it couldn't hurt to add more worms. I guess I might have to break down and put some macroalgae in the tank although I don't really like the way it looks in the display and I worry about it taking over. I'd love to attach a refugium/macroalgae tank but I'm tight on space and don't have anywhere to put one.

A couple more specific questions:
-Which flatworms are you suggesting? (I'm sure you know the species name!) I don't think I've gotten them in any of my booster kits before. Do you know who supplies them?
-Which cukes do you recommend for a system this size? I think the one I have might still be alive. It is about 3" long, brown with white spots and pointy projections off its whole body.

Best regards,
Robert

[rshimek]

Hi Robert,

The flatworms are always adventitious, where they come from I don't know. I know they have become established in my systems.

Without beating it to death, there are no suppliers of them, and flatworm identification beyond general group is simply impossible. I have at least 3 common species, and probably more. Several of them appear to be diatom eaters. I suspect they came in some live sand I got some years ago.

Your cuke sounds fine, from your description, it may be a Stichopus or a related bottom mopper.

[RobertK]

Thanks again, Ron! You're the best! :)