A crafty way a friend showed me years ago works well. It's VERY tedious and time consuming and frankly, can get nasty...but it does work.
Get yourself some air pump line. Don't get the really flimsy, cheap stuff...you wont be able to control it.
Then, you put that line down in the tank right up next to a bubble and siphon it. Get close to it and don't suck too hard on the line and it'll pop right off and stick to the end of the air line. Once you get it sucked up against the air line, just hold your toungue over the line to hold the vacuum. Pull it out of the tank, blow it into the garbage, repeat. Again and again and again....
It's very tedious as I said before, but it works like a charm.
Regards,
Tom