Colu

Ich are flat white spots not raised looks possible like the start of fin rot

I use a bucket remake To make the solutions and replace it each time so it's temperature match so it's no going to shock the fish

Sparkling gourami's gourami's are good center piece fish for smaller tanks you can keep them in small groups

A think a course of kanaplex in food and ick x to treat the water column will cover against fungal and bacterial infections and are plant safe

It could be internal parasites or constipation have you noticed any rapid breathing white stringy poop or flashing and has he pass any poop resently

Possible Epistylis recommend treatment is kanaplex in food if your using kanaplex in food you can still the water column with paracleanse to cover all bases

It sound like a swim bladder issue what I would do is Epsom salt baths 1 table spoon for 2 gallons for no more than 15 minutes twice a day for for 5 days as Epsom salt acts as a muscle relaxants to relieve pressure on the swim bladder if you see no improvement after that then I would treat with kanaplex in food feed a small amount twice a day for 7 days

Yes on a tank that size I would run both at the same time to avoid temperature fluctuations @Jacob Walsh

I would recommend getting two 150watt heater's for a 100 gallon stock tank and it's cover against heater failure if one goes out you have some backup I use to keep one Oscar in a 5ft tank along time ago they will move everything thing in the tank they have lots of personality bristlenose or other types of pleco would do fine with Oscar as long as they have plenty of hiding places

Could be a bacterial infections or ammonia burn with the red Gill's if it's a bacterial infections I would treat with kanaplex in food I would test your water for ammonia if you can as the co-op test 6 in 1 test strip doesn't test for that just in case something off

Probably nerite snail eggs

I would do Bolivian rams and nice group of Colombian blue tetras and a couple of Bristlenose pleco for algae control and a nice group of Cory's that you like I like orange Lazer Cory's

You could add some seachems purigen to your hob filter to remove any possible contamination it's possible the angelfish is just stressed in the new environment and needs time to settle down

Maybe you could sit down with them and explain the amount of fish in the tank is causing the illness in the Cory's and causing water quality issue and recommend that they get a bigger tank or re-home some of the fish

Could be a bacterial infection i would do a course of furan2 and follow it up with a course of kanaplex in food if your still losing fish after a course of furan2

As you have no nitrates your tank mite not have cycled I would keep an on that just in case you get any ammonia or nitrites spikes that will stress him out I would add some Indian almond leaves as they have antibacterial and antifungal properties to get the benefial effects you need to add 1 leaf per gallon Betta can change colour though out their life if he's lethargic and not readily eating I would do a course of maracyn if you can get him to eat as maracyn only treats external infection unless add to food I use a quarter of a packet of maracyn one table spoon of pellets one scoop of seachems focus 1 cap of garlic guard a few drops of water mix well feed a small amount twice a day for 7 days store any leftover medicated food in the fridge

The high levels of nitrates you have can effect a fish immune system I would do a 50 water change to get them below 40

It's a difficult one if he's still eating and active I would give him a chance

Flashing can be cause by parasites such as gill flukes ich fish also flash when ammonia is present or other chemical pollution active carbon dust from filter can irritate the gills on some if your seeing flashing every the your work past the tank then if more then likely parasites if it's just once I'm while I wouldn't worry

I would follow up with a third course of treatment to make they have been dealt with

It depends were your water comes from theirs always the possibility of lead copper or other metals in your tap water so I always air on the side of caution and use prime when doing water changes

That looks like it has rubbed some scales off if you think it's parasites have you noticed any rapid breathing white stringy poop your fish regularly rubbing on things in the tank weight loss

I had a single Oscar years ago and I kept him in a 5ft long tank that tank to small for large territorial cichlids I think an apisto or a group of small fish like x-ray tetras or neon and a bristlenose or nerite snails for algae control would work well or a single Bettas

Without noing your water parameters it difficult to no the cause a 5 gallon on the small side for bronze Cory's it's more than likely a bacterial infections caused by poor water quality or stress due to the overstocking I would treat with kanaplex in food feed a small amount twice a day for 7 days if you can test your water just in case something off such as high levels of ammonia or nitrites and post the water parameters that would be helpful

I no maracyn treats cyanobacteria am not sure that what it is maybe someone else with more experience of cyanobacteria can chip in