I started a marine tank and due to unforeseen circumstances had to opt out of it just at the point it was ready for fish and revert back to tropical fresh water. The marine tank went well with clean up crew and lots of copepod small bug things all over the live rock. Any way. I sold the live rock and clean up crew, gave the tank a very very thorough clean to get rid of any salts etc and filled it back up and put some bog wood in there. I used the same substrate but that also got a good rinse. Any way.... The tank seems to be fine, just some leaching from the tannins in the bog wood making the water a bit yellowy brown. I've also started to notice though some small bugs swimming around. Too small to photograph but they look exactly like the Copepods that were in the marine tank??! Is this possible? Could they be left over from the marine tank and thriving in the fresh water? Would they survive ? Or is this a hitch hiker from the wood? The woods getting a fluffy white covering too that I just wash off at water changes. I did use some stuff in a bottle that came with the tank called "cycle" that's meant to be full of good stuff. I'm sceptical but thought can't do any harm and put it in too. Any advice most welcome. Just curious really. I'm sure when some fish go in they will take care of these little critter......this is just more to satisfy my curiosity. I've had fresh water tanks befor but never noticed these bugs. Only in the marine. Thanks in advance. Ben.