Kuhli loach naughtiness

In my planted 40, I have three kuhli's--2 solids, and one striped. About a 2 months ago, I noticed that my solids had built a tunnel in the base of a plant--one with a dense root mass, so easily tunneled. I was a bit suspicious of what they might be up to in there, but minded my business and never thought about it again.

Then, at the last water change, I picked up a chunk of driftwood to clean beneath it, and was rewarded with a nest of the little buggers! Think there was at least 8-9 of the little guys--about 1 inch long, maybe 1/8 inch in diameter. Shocked the heck out of me. Now I'm concerned that the ones in my small tank here at work (a group of 5 stripers) may be up to the same thing.

Now I just wish I'd paid more attention so I could document what brought this on--I can't deal with too many more fish in that tank!

I can't even get a reliable count on the buggers--they are fast, and the babies only come out briefly for feeding. I'll see what I can do.

pH = 7.3
Hardness is mediocre (9/3), temp is around 78. Not heavily planted, but the plants are well established with a thick root bed. I think this is important, since I suspect they dug a tunnel into the root bed, using the roots to hold up the walls/roof. I feed every other day, a mixture of algae tabs, frozen community formula, blood worms, brine shrimp and scallops. I don't match water temps when I do water changes--water going in is about 60-65. Weekly changes of about 25-30%. Several pieces of wood, smaller gravel substrate, UGF with an AC 300 with sponges only.

This pair has been in the tank for well over a year. The parents were 2 of 3 I bought as buddies for a striped kuhli I've had for 3+ years (his companions passed on in a previous tank). They are about 2 inches long, and a bit bigger in diameter than a smiley ( ). The striped is much longer and fatter, so I think size must vary with the species.

This is my normal routine. Other than being a bit suspicious when I noted the tunnel they'd built at the base of the rotala, I can't recall anything unusual or different that I've done. About 2 months before this, I increased the protien I was feeding--instead of just blood worms, I added the scallops and chopped fish mix.

Wish I could be specific, and KNOW what brought this on.