I just lost about 50 waltl larvae after siphoning in some water last night from another tank. Both tanks are cycled and the water from both tested fine across the board. The only thing I can think of is the siphon bulbs I use are from wal mart (automotive type like for an outboard engine) and the one on this siphon was pretty new. Maybe it still had some manufacturing lubricant or some type of oil that blocked oxygen exchange. I've used them for years and never had a problem until now. Very frustrating.