Do the fish produce a stringy white poop?
How long after they start to lose weight, do they start having trouble remaining buoyant in the water?
-------------------------
Internal protozoan infection cause the fish to lose weight rapidly (over a week or two), fish continues to eat and swim around but not as much as normal, does stringy white poop. If not treated the fish dies a week or two after these symptoms appear. Metronidazole normally works well for this.
There is a medication (API General Cure) that contains Praziquantel and Metronidazole and might be worth trying.
It's interesting that API and the Californian government have listed Metronidazole as a carcinogen. That's a concern considering it was widely used to treat intestinal infections in people.
Anyway, handle with care, don't inhale the medication, and wash hands with soapy water after treating the fish or working in the tank.
-------------------------
The swimming problem has to do with their swim bladder not working properly. It's possible they have an internal infection that is damaging their swim bladder. Try Metronidazole and see how they go. One dumb question though, it is a 45 gallon tank with about 4" of gravel...how do I calculate the displacement of the gravel. I don't want to treat for 45 gallons when there is maybe only 40 gallons in there, right?
-------------------------
Do the following before treating the tank.
Work out the volume of water in the tank:
measure length x width x height in cm.
divide by 1000.
= volume in litres.
When you measure the height, measure from the top of the substrate to the top of the water level.
There is a calculator/ converter in the "How To Tips" at the top of this page that will let you convert litres to gallons if you need it.
Remove carbon from the filter before treating or it will adsorb the medication and stop it working.
Wipe the inside of the glass down with a clean fish sponge. Do a 75% water change and gravel clean the substrate. Make sure any new water is free of chlorine/ chloramine before it is added to the tank.
Clean the filter if it hasn't been done in the last 2 weeks.
Increase surface turbulence/ aeration when using medications because they reduce the dissolved oxygen in the water.
Monitor ammonia and nitrite levels during and after treatment. Metronidazole can wipe out filter bacteria and cause the tank to cycle. Do a 75% water change and gravel clean if you get ammonia or nitrite readings.
-------------------------
When filming with a mobile phone, turn the phone so it's horizontal not vertical, and the video will fill the entire screen, making it easier to see what's in it.