Colu

Wouldn't kill the one not showing any symptoms I would do a course of kanaplex just in case there's a bacterial component and you can put filter sponge on your intake pipe to prevent them getting into your filter

Neon tetra disease is caused by fish eating dead fish that have died in the tank and ingest to many pleistophora for there immune system to handle it can infect angelfish danios barbs guppies goldfish and other species of tetras it can remain dormont for upto a year it only when a period of stress weaken there immune system that you start to see symptoms what I would do is quarantine any fish showing symptoms so they don't die in the tank I would be very careful to avoid cross contamination by not moving fish to other tanks keep separate nets and equipment to avoid any potential issues if you have other tanks I would also add some aquarium salt to the quarantine tank 1 table spoon for 2 gallons to aid Gill function and add essential electrolytes if they go rapidly down hill and you think there suffering then I would humanely euthanize them with clove oil

Looking at pictures online I think it very good chance that you have psedancistrus genisetiger @Tedrock good ID @Johannes

The spots are two big for it to be ich it doesn't look like epistylis either what I would do is treat with a small amount of aquarium salt 1 table spoon for 10 gallons the salt will add essential electrolytes and aid Gill and do a course of kanaplex or maracyn2 which ever is more readily available just in case there's a bacterial component @Mr. Buzard

The one in the background look more like a leporinus could be two different species in the same picture or it might just be my eyes playing tricks on me

Looking at the bottom picture it looks more like a banded leporinus than distichous to me @mynameisnobody

The top one looks very similar to an electric Catfish @Aguinaga @mynameisnobody

A little more information would be helpful what are your water parameters ammonia nitrite nitrate pH etc any loss of appetite lethargy can you post a picture of the sick fish if possible @Firedashflame

If you have cyanobacteria the active ingredient in maracyn erythromycin will kill it finish the full course of maracyn water change and follow up with a full course of paracleanse cyanobacteria can cause oxygen levels to drop so I would make sure you have plenty of surface agitation to increase level's of desloved oxygen

No aquarium salt doesn't act as a muscle relaxant so it won't help relieve pressure on the swim bladder you need plain Epsom salt

Sorry for your loss

High levels of nitrates can affect fish's swim bladders weaken there immune system reduced appetite cause lethargy loss of colour adding quick growing plants such as hornwort or Elodea and floating plants such as water lettuce Amazonian frogbit red root floaters to help remove some of your excess nitrates coupled with increased water changes is the best way to reduce your Nitrate is your tank over stock are you over feeding are there excessive nitrates in your tap water all thing to look at @FishyJames

I would do a full course of broad spectrum antibiotic treatment such as maracyn maracyn2 or kanaplex which every one you have to hand than I would treat with paracleanse every 2 weeks for a total of three full course of treatment what your describing could be caused by a bacterial or parasitic infection

Sorry to hear that What I would do is a 50% water change once a week to keep your nitrate around 25ppm you could also add fast growing plants live hornwort or Elodea and floating plants such as water lettuce Amazonian frogbit to help remove excess nitrates so you don't have any issues in the future

What I would do is quarantine and treat with kanaplex and aquarium salt 1 table spoon for 3 gallons just in case there's a bacterial component I agree that doesn't look like columnaris@Elyse

Nitrate 50ppm is this before or after a water change as high levels of nitrates can affect the swim bladder if it's after a water change its possible you had a spike and that what affecting your angel fish @Tanked

internal parasites can cause swollen belly or an internal bacterial infection what I would do is a course of kanaplex or maracyn2 which ever is more readily available they are broad spectrum antibiotic treatment do one full course of treatment then give an update if your seeing no improvement clove oil is a human way to euthanize a fish or you can get a product called koi sedate he's some information on clove oil if you need to use @nemocura

I can't remember were I read it there a possible link between methylene blue swim bladder issues in fry apparently angel fish fry are particularly effected in the first couple of days after hatching have significantly higher level of swim bladder issues when exposed to methylene blue as it has mutagenic properties they recommend water changing out the methylene blue as soon as your the Frist fry hatch to avoid potential issues this could be the causes of what your seeing @monterey

Possible juvenile L001 looking at the spot pattern

Sorry to hear that at least you did you all you could for him

Could be genetic liverbears are prone to tumors due to low genetic diversity that can start with raised scales the fact it hasn't spread in the last couple oof months what you could do is quarantine and treat with aquarium salt 1 table spoon for 2 gallons and do a course of maracyn just in case there's a bacterial component given the length of time this has been going that's unlikely @Troy328

Any loss of appetite hanging at the surface lethargy flashing spitting food sunken belly any Redding to the Gill's

If your ammonia nitrite are zero and you have nitrate below 25ppm then water parameters won't be the cause the fact that you have fasted and done two rounds of kanaplex what I would do is Epsom salt baths 1 table spoon for 1 gallon for no more than 15 minutes for 5 days as Epsom salt acts as a muscle relaxant to help relieve pressure on the swim bladder @oarfish

As your seeing improvement keep going with the kanaplex after a course of kanaplex if your still having issues I would switch over to maracyn2

Possible L181 they do fine with a temperature range of 75-85 that shouldn't be a problem for them