Thanks for the complements, guys! I haven't seen this thread in about a year so I have to catch up...
Joei, I refresh the water about every two weeks, so acidity doesn't seem to be a problem, though I haven't measured it in a long, long time. If I don't refresh the water, the tank becomes dark with tannic acid since I'm not using a a charcoal filter (Yago, I prefer
not to as the darkening of the water prompts me to make those water changes!). I don't suspect any problem with water quality as larvae thrive in this tank and the newts are healthy (and laying more eggs...). Most of the leaves eventually decayed to the extent that they broke up and have been siphoned out.
Mark, Much of the soil has disappeared as well, the fine particles having been collected in the sponge filter. The substrate doesn't normally get siphoned as I only ever siphon the upper part of the left side of the tank, where there is hardly any substrate. Also, I don't siphon the other "wilder" side of the tank as I use a motor siphon and I have to be able to see clearly to avoid sucking in any of the many larvae in this tank. I feed and siphon on the left, though I sometimes drop a single cube of frozen bloodworm cube on the right side for the larvae to find.
Joseph, a judgment as to whether I damaged the environment would be subjective. It would depend on how much a purist one is. For one, the environment there is already extensively damaged by human activities. I doubt my collection of a small quantity of sand and gravel, a few rocks, and some leaves and branches had any significant detrimental effects, but the opposite could easily be argued. One could even say I damaged the environment by setting foot there in the first place. And then by walking through the forest, trampling on vegetation, spreading all sorts of alien pathogens. Not to mention bringing some newts back with me! So yes, I would say I didn't damage the habitat "to too much of an extent"
By the way, the moss, the driftwood and the plants (mostly
Egeria densa) in that tank are not from Okinawa. So it's just a semi-natural setup.
Leo, the dozen or so newts in there spend most of their time in the water but there are usually a few on land.