Black skimmers usally live near the water where thy can catch fish.
In Nevada
Black skimmers are not currently classified as endangered. However, they are considered a species of "Least Concern" on the IUCN Red List. Their populations may be threatened by habitat loss, disturbance, and pollution in some areas.
Skimmers are Silver Bream, not to be confused with Bronze Bream.
Is the skimmer plastic? Does it have a black bottom? If so, there is a kit for this. Check out black bottom skimmer repair - search.
Try another method of killing them.
No
by doing skimmers
The function of skimmers is to remove small pieces of food and batter that have already cooked so they do not contaminate the oil.
I just had change my sand filter and it seem working fine, but it doesn't have enough suction at the skimmers, why it does this?
fish, sea weed
None. Skimmers are mechanical devices, which use the surface tension of the oil to pull oil into a boat.
Do you mean leaf skimmers net that are attached to the pole? If so, Yes. The aluminum outer support ring just under the plastic wear sleeve will leave a gray to black line as you push it along the bottom of the pool. If the plastic cap or wear sleeve is worn on the outer edges, down to the aluminum that too is where the marks are coming from. If you are using the skimmer with the net inverted that too exposes the aluminum support bar. Ken