a few people try to use skimmers on FW
. they'll work better on brackish water.
the problem with FW
protein skimming is the water lacks proper surface tension due to lack of salt, so it won't foam properly, and little to no protein/organics are removed.
Some people do run a Surface skimmer on their FW
tank. This is like a pool or hot tub skimmer...its just grabbing floating debris from the top 1" of water...leaves, food, etc. Very very different from protein skimming.