What's this bug in my fish tank? How do I identify and treat it?

I am so sorry that you have had so much trouble with this! I didn't see that you included the type of tank you had (freshwater vs. saltwater) - the treatments can be different depending on the type of tank that you have. I also didn't see if you had definitively diagnosed that it was fish lice - there are not a great deal of parasites that are similar to fish lice, but if you haven't been able to have someone identify these parasites, I would recommend that it be a place to start. I am not sure what medical treatments you have attempted, but there are several that can be attempted. Some of them are oral treatments and some are treatments for in the water. Manual removal of the parasites is also possible. Given all of the things you have tried already, I would recommend evaluation of one or more of your fish by a veterinarian. They will gather information from you about your husbandry, and then will perform an examination on your fish. This will include evaluating samples of the gills, the skin, and of the parasites under the microscope. Your vet can then assist in helping to guide treatments and decide what is best for you and your tank.

It sounds like they have "ich". Here is a good video about ich that should answer most of your questions. ( https://www.youtube.com/watch?v=gVwyOifCRHI ) I suggest you talk to an aquarist in your area to get some medication. ( https://www.yelp.com/biz/aqua-life-aquarium-rocklin-2?osq=aquarium+store ) Hope this helps. Best wishes.

It certainly sounds like something is irritating this fish. Most often it is caused by parasites, usually ich. With ich you sometimes see salt like spots on the fins, you also may see a dusting in the dark if you shine a light. Other things that could cause itching would be irritants such as high ammonia levels. Personally I do not like adding chemicals to the water, especially not with other species such as snails and shrimp. To treat ich you can simply increase the water temperature and you can bathe the individual in salty water.

Those could be copepods. They are typically harmless and difficult to completely eradicate. On the good side, they are a sign of a healthy tank and are useful in eating decaying matter in the aquarium. The brown algae can be due to insufficient lighting or lighting periods. You can wipe down the glass and plants, perform a partial water change and increase lighting. It can take weeks to month to resolve. Use only aged or conditioned water that is temperature matched to prevent stress or shock. Confirm stable water chemistry and quality. Make sure the water temperature is correct as well. Too warm or too cold can cause stress. Look the Jack Dempsey over for signs of injury or infection. Ich, bacterial infection or fungal infection can cause the fish too twitch or shiver. Plain aquarium salt (NOT table salt or Epsom salt) dissolved at 1 tablespoon per 5 gallons of water is a great general tonic that can reduce stress, improve gill function, treat minor infection and aid in any recovery. The eels should be fine, but the snails should be moved temporarily. You can relocate both to a separate tank to be completely safe. Treat the tank for 10-14 days then reassess the condition of the fish. Perform a partial water change afterwards to reduce salinity before you returns the eels and snails to the tank.

By your description, it could be a species of isopod. These are typically not dangerous to tank inhabitants. The best option is to empty the tank and sanitize it. Use completely new substrate and monitor humidity levels. Keep the tank clean of stool and remove any uneaten food or dead/drying plants to prevent attraction of pests.

It is not uncommon to get external parasites living in aquariums. For example anchor worms are really common and will bury into the fish leaving a white trail hanging out. I would suggest changing 70% water to reduce parasite and eggs, clean your filter and then treat the water with bettafix or bettazing which helps to kill parasites. Be careful you arent overfeedibg as this can encourage parasites.

Check the water chemistry. The discoloration could be due to elevated ammonia levels which can cause "burns". Use a home test kit or submit a water sample for testing. The local Petco may do this for free or for a small fee. Aim for an absence (0 ppm) of ammonia and nitrites with nitrates at 20ppm or less. Perform partial water changes to stabilize chemistry and/or to improve water quality. Use only conditioned water that is temperature matched to prevent stress or shock. The Neons (blue fish) appear to be infected with Ich, a parasite. Treatment is possible with commercial products found in the local Petco. Follow label directions carefully. You will need to treat the entire tank until all traces are gone. Removing a lump from your fish on your own is never recommended. You can cause severe injury. Most broad spectrum antibiotics (Kanaplex, Maracyn, Maracyn 2, etc.) found in the aquarium section of the local Petco should help treat or prevent infection. Choose one and follow label directions. Remove the carbon filter insert during treatment if indicated. Maintain pristine water quality via filtration and regular partial water changes to aid in recovery. You can feed frozen worms, just thaw then first in a small cup then place them in the tank.