Its funny... I only just noticed my first MTS in my tank perhaps 3 weeks to a month ago... and upon re-scaping some of my tank to accomodate my new piece of driftwood, I noticed a good number of them. (perhaps a dozen or so... I kicked up maybe 15-20% of the sand bed) In all fairness, they're neither an eyesore, nor do they seem to affect anything else negatively. They do seem to go after a little bit of the algae on the back wall of my tank, and have helped clear up the bit of algae that was on my large piece of driftwood. I'm rather glad to have them help aerate the sand bed in my tank, as it gives me some assurance that I'm not building up any toxic gasses which might harm my fish.
I will say though... a couple of them have gotten BIG! The one I was watching just a couple of nights ago must be 1.5" easy. The population isn't particularly large to what I can tell, but they do have a food source. (algae in the tank) I don't see myself as one who over-feeds... my fish typically get everything I put in the tank within 3-5 minutes anyway.. and my discus/catfish are always on the prowl for more food. Would be nice if the MTS were easier for them to munch on, just to get another free source of food going. :
I had some really tiny ones vac up today. I noticed them at the bottom of the bucket once I dumped it out. most of them will only go half way up my nozzle and not through the tube.
This morning I found a few at the very tops of my plants.