Colu

I agree sounds like something wrong with your water parameters such as high levels of ammonia nitrite or nitrate or you pH and KH could be to low that why you had a mass die off of your guppies and Molly with out noing your water parameters ammonia nitrite nitrate pH kH it difficult to diagnose if it were ammonia or nitrate or nitrite poisoning the most effective treatment is aquarium salt 1 table spoon for 1 gallon it help to speed up the removal ammonia from fish blood and it acts as a natural barrier thought chloride ions to prevent the uptake of nitrite and nitrate @ScandiDefense

Your water parameters are fine have you added any new fish to the tank recently if so did you quarantine them before adding them to the main tank

Yes you can use aquarium salt with kanaplex

Chinese algae eaters can feed on the slim coat of fish this could have happened in this case with the redding to the body and the hole it could also be a bacterial infection what I would do if you can is quarantine and treat with a broad spectrum antibiotic treatment such as kanaplex or maracyn2 and add a small amount of aquarium salt 1 table spoon for 5 gallons @Marcelo

If it's been a month with these spots it's more than likely not epistylis did you quarantine the flag fish before adding them to the main tank if no they could have bought in parasites that would explain the odd random deaths weeks apart I would Keep treating with paracleanse every two weeks for a total of three full courses of treatment I would quarantine the black neon tetra with the spots and treat with aquarium salt 1 table spoon for 1 gallon for 7days @Hanneke

Do you have a heater and filter on his tanks as bettas do best with there temperature around 82 low temperature can cause loss of appetite

Have you got a picture of the fish it with the a diagnosis spots as the raised spots could be epistylis he's how you tell the difference between ich and epistylis @Hanneke

You can add it to repashy or mix it with pellets or frozen foods

With nitrate poisoning it can cause a condition none as brown blood disease this happen when a fish's bloodstream is contaminated with nitrates Turing a fish's blood dark brown this prevent the red blood cells from efficiently absorbing oxygen from the water this is why your fish is hanging at the surface it also cause reduce feeding response weaken immune system leading to secondary infections salt is the most effective treatment for nitrate poisoning 1 table spoon for 1 gallon increase surface aggregation try adding a small amount of seachems garlic guard to her food to try and stimulate her appetite I would leave her were she is for now in her weaken state moving her will be more stressful @AquaAries

Just the black carbon filter pad

Active carbon absorbs the medication so the medication wont have any effect on the disease your treating while you have active carbon in the tank so just remove the carbon pad from your filter and leave your filter running during treatment ich causes massive electrolyte loss so I would add a small amount of aquarium 1 table spoon for 5 gallons the salt will add back in essential electrolytes I would always add an extra air stone to increase the levels of desloved oxygen as medication change's the viscosity of water lowering the levels of desloved oxygen @Izzyf

Without noing your water parameters it's difficult to make an assessment as most case of disease are caused by poor water quality incorrect temperature to low or high poor diet

What are your water parameters ammonia nitrite nitrate pH temperature @Sergio

I wouldn't recommend use maracyn2 and kanaplex together I would just use one of the medication mixing medication can be harmful to your fish in certain circumstances and be stressful to your fish I would just do a full course of kanaplex and I would add some aquarium salt 1 table spoon for 3 gallons the salt will aid Gill function and add essential electrolytes

From my experience paracleanse is safe medication as long as you follow the dosing instructions on the box i haven't had any side effects when I have used it to treat my fish in the past Theirs a small chance it will harm your benefial bacterial so I would test your water parameters more frequently during treatment

I vote for Bolivian rams very under rated fish and colour up really nice once they get older

Looks like corydoras aeneus bronze Cory's

Looks like a bit of a sunken belly that can be a sign of a parasitic infections you will get the odd random deaths weeks apart that would explain your other fish losses what I would do is treat all the fish with paracleanse every two week for a total of three full courses of treatment @flyingcow

With crushed coral you want to add 1lb per 10 gallons it desloves more quickly in acidic water I would start at half a pound of crushed coral per 10 gallons and see were your pH stabilize at you want some kH to prevent your pH from fluctuating

With the symptoms your describing I don't think it's columnaris that usually kills fish with in 24hr to 7 days depending on the strain paraguard is only effective at treating ich for velvet or flukes I wouldn't recommend using it what I would do is a 30% water change and run carbon for 24hr before dosing paracleanse you can use maracyn with paracleanse I don't recommend mixing medication it can be more stressful on fish and they require water changes on different days when doing full course of each

It could be I don't trust test strips when it come to. pH or kH mine always read 0 kH and pH 6.2 when I test with my pH pen and API kH test kit my kH is 4 and my pH is 6.8-7.1 Cory's should do fine in a lower pH and KH if it's causing the pH to fluctuate them that can be stressful

As antibiotic treatments haven't had much of an effect I would stop treating with them as over use of medications can have a negative effect on your fish and the chewing action your describing can be a sign of a parasitic infection what I would do is treat with paracleanse every two weeks for a total of three full courses of treatment

I would do a daily 30% water change and redose the medication daily for the full 5 days it should be safe for your other Cory's if you have a quarantine tank I would the sick fish on its own @eusher11

Looks like saprolegniasis it's caused by water mold it's usually secondary to a bacterial infections most effective treatment is a combination of of malachite green and an antibiotic treatment such as maracyn or maracyn2 to treat the underlying bacterial infection @eusher11

It's difficult to say what going a little more information would be helpful what are your water parameters ammonia nitrite nitrate etc what other fish are in the tank any other fish displaying odd behaviour rapid breathing listlessness hanging near the surface @Nanci B