Colu

If you have a quarantine tank I would treat on its own if you don't I would just treat the main tank following the instructions on the medication @Ryan1988

Looks like a fungal infections what I would do is treat with ick X active ingredient malachite green is effective at treating fungal infections and I would add a small amount of aquarium salt 1 table spoon for 10 gallons @Dyzir13

As you haven't added anything new to the tank it could be bacterial infection causing the symptoms your seeing what I would do is a course of kanaplex or maracyn2

From what I have read neon tetra disease can survive for months without a host in your aquarium it can infect Rasboras danios barbs guppies angelfish goldfish other Tetra species It's best to bin all the substrate and plants any hardscape that can't be disinfected and disinfect the tank and equipment with a 3% hydrogen peroxide solution leave it to dry then I would repeat the process again then I would fill the tank add a filter add hydrogen peroxide solution to the tank and leave it 24 HR then it will turn into H20 and oxygen just to make sure there's no chance of reinfecting any new fish you add to the tank in the future @Ramplo

Have you added anything new to the tank recently that could bought in disease

It does look thin What I would do is treat with Expel p once a week for 3 weeks and I would follow up with another 2 course of paracleanse in 2 week apart that will treat most commonly encountered parasites @Brandxn

Any rapid breathing listlessness hanging near the surface loss of appetite @Ryan1988

It could be weak and it's struggling to swim against the flow of your filter if you can't quarantine I would try and reduce your flow from your filter

Looks like an injury or a bacterial infections if it turns up and still has the red area to its belly I would start treating with kanaplex or maracyn2 add an extra air stone during treatment as medication lowers the level of desloved oxygen in the tank @BenJames3445

What I would do is a course of kanaplex then follow up with Expel p once a week for 3 weeks just to make sure you have dealt with the issues in the previous thread

What are your water parameters ammonia nitrite nitrate temperature with the black on the fins it could be ammonia burn till I no your water parameters it difficult to say for sure I would add an extra air stone and some aquarium salt 1 table spoon for 2 gallons that will aid Gill function and add essential electrolytes till you can test your water parameters

If I remember correctly these worms have a symbiotic relationship with crayfish and don't infect fish someone correct me if am wrong if it's hole in the head you want to treat with metronidazole in food that why I recommended metroplex as these fish came from a pond what I would do it is treat with metroplex in food and treat the tank with praziquantel

It could be the start of hole in the head even with the slightly raised spots what I would do is a course of metroplex in food feeding a small amount twice a day for upto 3 weeks

Fish's stomachs are the size of there eye ball that what I use as a reference when feeding depending on the size of tank and how many fish you would be adding that would denote how much food you would be adding in to the system

I always find it difficult to tell the colour with the API ammonia test kit that why I use a Hannah instruments digital ammonia tester sometimes mine looked like it had a slight green colour but my digital tester always tested zero for ammonia hopefully kanaplex and jungal fungus clear fizz tabs does the trick @HelplessNewbie

What are your water parameters ammonia nitrite nitrate etc temperature have you added anything new to the tank recently any rapid breathing listlessness hanging near the surface flashing spitting food out weight loss lack of appetite @xerf9

Looks like epistylis it feeds off of gram negative bacteria on the slime coat of your fish and spreads more quickly at higher temperatures causing secondary bacterial infections that what usually kills your fish what I would do it s start dosing the tank with maracyn2 and add aquarium salt 1 table spoon for 3 gallons the combination of two is very effective at treating epistylis @Arden

I would Quarantine and treat with aquarium salt 1 table spoon for 2 gallons for one week @TheMilkman

Looks like internal hemorrhaging you can get that from a injury bacterial infections parastic infection possible hemorrhage septicemia if you haven't already I would do the course of kanaplex and jungal fungus clear fizz tabs containing nitrofurazone following the treatment plan I would do to full courses of treatment back to back @HelplessNewbie

For Epsom salt baths 1 table spoon for 1 gallon for no more than 15 minutes for 5 days is what I usually recommend aquarium salt I would start at 1 table spoon for 3 gallons and up in a couple of days to 1 table spoon for 2 gallons if your not seeing any improvement

I agree with @Fish Folk@nabokovfan87 add some aquarium salt 1 table spoon for 2 gallons and do a course of kanaplex or maracyn2 just in case there's a bacterial component you can add some botanicals as well

Looks like she full of eggs I don't see any pineconing have your noticed any rapid breathing listlessness hanging near the surface reduced feeding response if you haven't I wouldn't treat I would just monitor more than likely full of eggs with in a couple of days she will release her eggs and bloating should go down or she just fat thought over eating @Ron Uni

I agree with @Odd DuckI would follow the advice given

I would cut it so it fits the full length of the tank if you want more surface agitation as a rule the shorter the spray bar more flow

I would switch to treating with kanaplex and jungal fungus clear fizz tabs as you still have issues that provides a more broad spectrum antibiotic treatment