Colu

Most Otto's are wild caught I would always recommend quarantining them and treating for parasites preferably In a well seasoned tank if that isn't an option you could leave rocks or wood under a bright light or in a tub out side to grow biofilm and add new piece's each day to the tank

Nerite snails are fine with salt they need it to breed if you don't have live plants I would up the level of salt to one table spoon for 3 gallons that should help reduce any possible fluid buildup in the eye if after a week your seeing no improvement or it's getting worse then I would do a course of maracyn2 in food feeding a small amount twice a day for 7 days as Popeye can be caused by a bacterial infection active ingredient minocycline also has anti-inflammatory properties

If you have some pieces of wood covered in biofilm you could transfer to the quarantine tank every couple of days replace the piece of wood with another piece

It can be stressful better to are on the side of caution if you think anything wrong with your fish

You need a minimum of 1 table spoon for 2 gallons of aquarium salt to treat ick I would add the aquarium salt as ich causes massive electrolyte loss and the salt will add back in essential electrolytes and keep treating with ick X the combination very effective for treating ich here's how you tell the difference between ich and epistylis if you not sure what your dealing with @ckylesworld

Typically when filter and air stone get the desloved oxygen to 9.5ppm adding another air stone has very little affective on the levels of desloved oxygen whether your using a diffuser or a sponge filter with out an air stone it shouldn't be able to get the levels of desloved oxygen to the point that harmful to your fish

I would say that a guppy fry

Doesn't look like gas bubble disease is usually caused by supersaturation of oxygen most tanks running a filter and air stone will have between 8-9.5ppm of oxygen that not enough to cause gas bubble disease it's more than likely trapped air bubbles on the fins from were he has swim thought the air stone i have seen it in Bettas or longer fined fish before they can stick to the fins for hours even if the fish moves I would turn your air pump back on I do think it's anything to worry about @Lennie

I would add an extra air stone if their hanging at the surface and some aquarium salt 1 table spoon for 2 gallons that will aid Gill function and add essential electrolytes I would keep doing large water changes and add a double dose prime or Fritz complete @Ninjomasuggested to help detoxify any ammonia till it constantly stays at zero @Ridwaan98

It's a combination of things they arrived on Thursday at petsmart weren't quarantine and possibly put in tanks with already sick fish and immediately sold and bought back to your tank all that stress can weaken a fish's immune system you can get delayed mortality syndrome were fish die hours or days later due to all that stress or develope secondary infection did you use a water dechlorinator when you did an initial water change also if this is your only LFS I would consider ordering fish online in the future if I go into a LFS and they have multiple tanks under going treatment and they don't quarantine that's a red flag for me I wouldn't buy fish from them it's to much of a risk @evonner

Looks like a tumor they are really common in Bettas due to inbreeding treatment wise theirs no a lot i could suggest if he's eating ok and active and seem happy I would just let him live his life if he gets to the point you think he's suffering I would humanely euthanize him with clove oil @Liddojunior

Those colours are just stunning I think they become more widely available if they lived longer

Genetic deformities are common in guppies due to inbreeding that can cause hunch back not eating or spitting food out and wasting such as developing a sunken belly that's more than likely wasting disease the fin fraying can be caused by other fish nipping the fins of your guppies

As long as they only do it occasionally it's ok if there doing all the time then I would be concerned fish often do this when theirs high levels of ammonia or nitrite can cause fish to flash and ich and other external parasites such as Gill flukes I would always check my water parameters first before anything else

Melafix is oil based herbal treatment its not good for the labyrinth organ of gourami's it only works as a mild antiseptic treatment at best if you have it to hand I would start treating with aquarium salt 1 table spoon for 2 gallons till maracyn arrives @macdaddy36

If the lump sinking it could be a fluid filled cyst or an injury that caused some inflammation of tissue around the mouth I would still do the week of salt and monitor you could get a bleeder value for air pump to reduce the air flow coming from the pump

A little more information would be helpful what are your water parameters can you post a picture of the sick fish any red patches or white lips on any of your fish @GinkoTracks

Possible injury that caused the ulceration looks like a secondary bacterial infection I would do one full course of kanaplex and I would add a small amount of aquarium salt 1 table spoon for 5 gallons that will help reduce any possible fluid buildup in the lump aid Gill function and add essential electrolytes @Goshfush

Lumps on the mouth can be caused by number of things so it difficult to give a definitive diagnosis give me an update after a week of salt if theirs no improvement or it gets worse

It difficult to off your picture but it looks more like a lump what I would do is quarantine and treat with aquarium salt 1 table spoon for 1 gallon for one week @PerceptivePesce

Have you got a picture of the fry does it have a fuzzy appearance or just look like a white patch on the mouth

The colours in the bottom picture remind of a dace

You could try putting an air stone in the affected area to help increase flow

I have seen this with my bristlenose many times over the last twenty years its usually caused when the male traps the female in a cave and she rubs off the scales on her back I usually add some Indian almond leaves and a small amount of aquarium salt 1 table spoon for 5 gallons it usually heals with no need for further treatment @CJs Aquatics

Mine is my 13 year old comet goldfish