Folks.......I don't have anything scientific to say but I have been working with the "black" tubifex worm( I don't think they're tubifex) since about 1968 or so when I was a young brat working at a pet store and going to Purdue University. The pet store dealt with both the red and black tubifex worms as food for fish. The red worms were impossible to work with......no matter what we did, the worms were dirty and NEVER cleaned up like the black worms did. It wasn't but about 2-3 months and we stopped dealing with the red worms. The black worms were put in a 2-3 gallon pail and put under a faucet and water was slowly run over the entire clump of worms for 1-2 hours a day for several days.....sometime less and kept in the 'fridge. After 2-3 days usually, unless someone left them out they stayed clean virtually forever as long as someone would wash them at least every day....that's where I learned to keep them. Back then, 1968 I could spawn about anything I wanted to....people thought I had a line to the fish GOD.......I was using black worms....fish will spawn after eating black worms, given the right water conditions.....fish were created to spawn....they want to do that. Over the years.....30....... I have just stayed quiet and spawned virtually any fish I wanted, within reason, because, I think, I have ALWAYS used black worms. I must admit however the years I was doing and spawning and raising discus I chickened out and ONLY did beefheart and other discus food. But I firmly believe that if the worms are cleaned properly and cared for there will be no problems.......I cannot attribute any fish problems that were for a fact caused by the black worms, and that has been for 30 some years!!!!! These days I buy them by the fistful.......it costs about $15-18 for a fistworth. I put them in an appropriate tupperware dish....straight sides and about 6-7" diameter and maybe 6" high......and I will wash the worms 2-3 times a day for the first 5-6 days and I will NOT feed out of this batch until the water in the worm bowl is as clean in the morning as it was the previous night. I keep the worms in the refrigerator always.......let the ball of worms settle down in the tupperware after rinsing them vigerously, as soon as they spread out in the bowl put just enough water in the bowl so that you can see the worms wiggling at the surface of the water.....don't just submerge the whole bunch.....I don't know why that works it just does. Now depending on how many I feed, it may be 2-3 weeks before I've used the whole batch up. I have live daphnia, hatched baby brine etc. I'm ashamed to say my dwarfs won't eat a flake....they don't know what it is. ..........but guys don't tell anyone that I do this.....they all tell me I will kill my fish.........for 30 years they've told me that......someone was over the other day and said "...I don't know how you get your apistos so big........mine, he says just won't grow on flake food......heh, heh, heh.........He thinks daphnia is stupid too!!!! You folks have a good weekend.....won't be back till Monday......no internet at home.......will be looking forward to all of you telling me I can't use black worms it causes BLOAT. .......TGIF Mike