Is this ich or Lympho?

[Jay Hemdal Verified Community Expert]

Will hypo salinity stress out the fish or harm them? Also would it affect copepods and bacteria and stuff

All ich treatments have some degree of risk for the fish. You are trying to kill the parasites without killing the fish. A specific gravity of 1.009 will do that. However, 1.008 will be too low for some fish and 1.010 may not stop the ich.

Hyposalinity will not harm your beneficial bacteria, but it will kill most invertebrates, including copepods. it may also kill some types of algae.

Jay