Join Date: Jan 2013
Location: Cartersville GA
If you didn't treat the plants before you rebuilt your tank, whatever was on them is now in it again. Cut back on the light a little; algae thrive on excess light and food (found this out myself the hard way). Also, what, if any, routine maintenance were you doing on the tank when the shrimp started dying, and were you keeping up with water parameters (ammonia, nitrate, nitrite)?
I don't mean to nitpick; just helps to know what's going on before offering advice or a solution. Don't know if they were the same as what you have, but I had some kind of gross, tiny little white worms in my 2.5g tank a month or two ago, and got rid of them with partial water changes and taking a gravel vac to it to get the nasty stuff (plant and snail litter mostly) out. As long as you keep the water clean and don't overfeed, they should stay away.