Skin, fins, mouth, or eye problems:
Swelling or bleeding: Swollen abdomen, red coloration due to bleeding at the base of the fins, under the skin, eyes, or around the vent aka anus. (systemic bacterial infection. contact extension)
No or slow growth. (problem with the feed, either the quantity being fed in relationship to the biomass* or standing crop* of fish or the nutritional quality of the feed may be marginal)
Thin and emaciated. (lack of nutrition, increase feed)
Unusual:
Spinal deformities (scoliosis, lordiosis contact extension)