Do black kuhli loaches eat Malaysian Trumpet Snails?

[Pangiophile]

I recently added some black kuhli loaches (P. oblonga) to my community tank and have started finding empty snail shells on the sand. The shells vary in size up to almost an inch. There haven't been any other changes or additions so the loaches seem likely suspects. I haven't caught them in the act of eating a snail, but I did see a possible attempt. The MTS was upside down on the sand and had its foot fully extended to try to turn over, and the kuhli suddenly lunged. The snail retracted its foot very quickly and the kuhli swam away. Did he get a bite perhaps? Enough nips might kill the MTS and the loaches could clean out the shell.
The pet store folks told me that they'd had the loaches in their tank for around 6 months and I wonder if that was when they learned to hunt snails (there's no shortage of MTSs there).
Just wondering if anyone else had seen this before with black kuhlis (google search was inconclusive).

[mikev]

Interesting...

no mts here.

p.oblonga will eat a ramshorn if its shell has been broken and may try attacking a live snail but I have not seen any successes. (Some corydoras would try this too btw).

I guess the instincts are there and if you try often enough you may eventually succeed....

[Pangiophile]

I'm 99% convinced that the loaches are eating the snails. Normally a few hours after lights out, the tank would be crawling with hundreds of snails of varying sizes. Just now, I could only find one.
This also explains the change in eating habits. In quarantine the loaches were eating sinking pellets very eagerly. Since moving to the community tank they haven't been that interested. I just thought they were getting a lot of leftover flakes, but now it seems more likely that they've just been enjoying the snails more. I guess now that the snails are more or less wiped out, they might become interested in the pellets again.

[Diana]

I have had tanks with small Loaches. Kuhlies, sids and zebras. Mostly there were pond snails in these tanks (much softer shells).
The Loaches can easily manage to eat baby snails, but my Loaches seemed not to bother the adult snails, so I constantly had new litters of baby snails for the Loaches to dive into. However, if your Loaches are attacking the larger (reproductive age) snails then I would guess that your snails are not going to survive much longer.

[mikev]

Sids and Zebras are botine loaches, they have the equipment for eating snails, so no big surprise here.... for a kuhli to crack an mts shell would be an achievement.....

One more thing remembered: I've seen lh.disparis (hillstream loach) going after baby ramshorns.... and my pg.laticeps were seen eating pond snail eggs (yuck.... but it does not seem to harm them).

[Pangiophile]

Just to explain more fully, the shells are not cracked. Somehow the MTSs are being killed and the shells cleaned out from the opening. There seem to be some snail bits deep in the shells that are not being reached, but the snails are definitely being eaten. I can't say for sure that the loaches are killing them since I haven't seen it happen. There doesn't seem to be another explanation, though.

In this tank I used to have around half dozen reproductive adults (3/4 inches long or so) and a few hundred snails of varying sizes. Last night I could not find any of the adults and only one of the smaller ones.

My thought is that the loaches might be nipping the snails when their feet are out and they're cruising around looking for food. Sure, the MTSs can retract into their shells and be safe, but they've got to come out and eat some time, and the loaches can be patient.

I don't think any of the other inhabitants could be responsible. We have some neon tetras, one betta who hasn't shown any interest in the snails (and anyway sleeps at night when the snails are out), and amano and ghost shrimp.

The water conditions seem fine for MTS (general hardness is 10 degrees, kh is 6, and pH stays close to neutral with CO2 supplementation). Anyway, the word around the 'net is that MTSs thrive in almost any freshwater conditions that support fish (and the fish are all fine). Nothing has changed other than adding the loaches recently.

Any other experiences out there? It sounds like this might be very unusual behavior for black kuhli loaches. Maybe there's another explanation but nothing plausible comes to mind.

In the mean time, I might need more shrimp to keep up with cleaning the tank. The MTSs were doing a good job on dead leaves, fish poo, etc. and now it's starting to build up.

[Diana]

I think you are right. The Kuhlies are nipping at the MTS when they come out to feed, and end up killing them.

[Pangiophile]

Should I be worried that the MTSs may be rotting in their shells since the kuhlis can only reach so far into the shell? I pulled out a couple big shells and there seems to be quite a bit of snail left inside. Probably not good for water quality...

[Pangiophile]

I might have spoken too soon... I just did a water change yesterday, and today suddenly there are good amounts of MTSs again. I'm really glad to see my cleanup crew back at work, but am trying to understand what might have happened. It had been a month since the prior WC but the water parameters were decent (20 ppm nitrate / 0.5 ppm phosphate). GH is 10 degrees normally, though I didn't check before the WC. I also didn't check pH.

Might the water have gotten into some kind of condition that killed off a few MTSs and drove the rest into hiding? The fish and plants all seemed fine so it is hard to think of what could've caused the problem. Maybe a combination of acidification and mineral depletion, which would be bad for their shells? The plants grow fast and I dose traces and iron, and nitrate and phosphate sometimes, if they get low, but not calcium or magnesium.

Any other theories? I thought MTSs were nearly unkillable (other than by predation) but seem to have stumbled on something that did the trick.

[NancyD]

I had quite a few empty MTS shells, too, in a tank with black (oblonga) & striped (semicincta?) kuhlis & also vaillantella maassi loaches. I wasn't sure is it was my soft water or maybe the loaches eating some. The MTS were never eliminated & I never saw any actual predation so I don't know...