Colu

With what describing there starting to relax in there new tank and come out more paraguard safe to use at full dose with corydoras am struggling to see any fungal infection on that Cory do you mean the yellow spot on the tip of the fin @sharkbaithoohah

Yellow powder is usually nitrofurazone that antibiotic treatment that predominantly treats gram negative bacterial infections you should be able to get Esha 2000 that is effective against mild bacterial infections hopefully you won't need to treat I would have some medication to hand just in case

When you test if your water parameters are fine then it looks more like an injury you would have to monitor very closely just in case it develops a secondary bacterial or fungal infection you could add some Indian almond leaves as they have antibacterial and antifungal properties you might have to add one leaf per gallon to get a beneficial effect if you notice it get worse then I would do a course of kanaplex or maracyn2 Which ever one is more readily available @EggShappedFish

loricariidae.com have a lot of useful information@Epiphanaea

Yes he would start to show some of the symptoms I mentioned there currently no effective treatment for mycobacterium other than euthanizing any affected fish and sterilisering the system it highly infectious and would have infected some of your other fish poor genetics or old are more than likely the cause in this case

From what I have read about L276 in the wild they are found in temperature ranging for 78-88 so your tank is going to be to cold for it that can lead to a lot of health issues

Possibly melanotaenia herbertaxelrodi

It could have multiple causes such as poor genetics mycobacterium is really common in rainbow fish that will also cause abdominal swelling odd swimming patterns weight loss skin ulceration some old rainbow fish can develop a humped back @own_highway_somerandonumbe

Platys like the same water parameters as mollies neon tetra will be fine with those water parameters as they have been captive breed for a very long time they can adapt to a wide range of parameters @Pleasetrythefish

What are your water parameters ammonia nitrite nitrate pH KH GH temperature any thing Sharpe in the tank that could have cut itself on @EggShappedFish

if your seeing nitrite you more than likely have ammonia your pH should 7.5 for mollies your KH is to low what I would do is daily water changes and add a double dose of prime to help detoxify any ammonia and nitrite till your nitrite constantly stays at zero I would add crushed coral to your substrate or a media bag to raise your KH and pH you will need to add one pound of crushed coral per 10 gallons i would Also add a small amount of aquarium salt 1 table spoon for 5 gallons just remember to only put back in what you take out so if you do a 5 gallon water change put 1 table spoon of aquarium salt back in as salt only removed though water changes @Pleasetrythefish

Sorry for your loss

I would leave in quarantine it at least two weeks with out any issues before moving her @ravvlet

What are your water parameters ammonia nitrite nitrate pH KH GH temperature and what symptoms are you seeing @Josh D

If it's a swim bladder issues you would want to treat with epsom salt baths 1 table spoon for 1 gallon for no more than 15 minutes for 5 days as Epsom salt as a muscle relaxant to relieve pressure on the swim bladder @ravvlet

It could be caused by an injury but a couldn't rule out a bacterial component I think it would be worthwhile doing a course of kanaplex and add a small amount of aquarium salt 1 table spoon for 10 gallons@Stef

Sorry for your loss

Agree snail eggs

Have you noticed any aggression maybe the other two are bullying it stopping it eating if there's no aggression what I would do is @Odd Duck treatment protocol for parasitic infections you can use paracleanse instead of prazipro

What are your water parameters ammonia nitrite nitrate pH KH GH temperature any rapid breathing hanging out near the surface lethargy flashing spitting food sunken belly white stringy poop @Monkeypoint

Could be the start of hole in the head for that you would want to treat with metronidazole active ingredient in metroplex or fritz metrocleanse feeding a small amount twice a day for upto 3 weeks it safe to use with ick X if your using it in food

How quickly it's come on more than likely to have injured itself keep him in quarantine with epsom salt if it's broken it's back or other internal injuries it probably won't recover

With ich you want to treat for three days after you see the last spots and add some aquarium salt 1 table spoon for 5 gallons as ich causes massive electrolyte loss and the salt will add back in essential electrolytes just remember to only put back in what you take out so if you do a 5 gallon water put 1 table spoon of salt back in if your not seeing any spots on your other what I would do is add one dose of ick X in and let it marinate for a week as a preventive treatment @Michaeldv2

What your KH and GH any rapid breathing hanging out near the surface lethargy flashing spitting food out sunken belly @Sheargrub

What I would suggest is quarantine the fish with white spots and treat with aquarium salt 1 table spoon for 1 gallon for two weeks do the third course of praziquantel if your still having issues I would do a course of expel p if you notice the fins are less clamped than I would follow with a another course on week 2 third course on week 3