To clean out the tank, try making your own siphoning tube by getting some small tubing. Airline will do the job too, but it's VERY slow, hehe...but it is safer than something bigger, you can slowly move it around the bottom sucking up the yuk and if you see some fry approaching it, then put your finger over the other end to stop the suction until you get to a clear area again. A friend of mine who breeds Bettas made his own siphoning tube by getting some firm tubing a bit wider than airline tubing (the firm tubing makes it easier to vacuum then the airline tubing), and attached it to airline tubing with silicone. He says it works wonderful, I'll be making something like that soon.
Let us know what you do and how it works.
Linda