I know you are being bombarded with what to do and by no means do I know what your fish has, just some info on what I have done in the past for ich and a flat worm explosion in my tanks. (I used a 50 gallon rubber made tote for larger fish with PVC fittings) I used this process with great results, any info I feel is beneficial
Hyposalinity How-To
Hyposalinity or Hypo, is the process of gradually lowering the salinity of your water to a range of 12-14%, or to a specific gravity of 1.008-1.010, 1.009 being the ideal level. Then holding it there for 4-6 weeks.
Hyposalinity will disrupt the life cycle of Marine Ich. If Ich cannot complete its 4-stage life cycle, it cannot continue to infect our fish. There are conflicting reports as to which part of the cycle is killed. Some say it will cause the Theront (free swimming/infective) stage to rupture, killing it. Some say it causes problems in the Tomont (encysted/reproductive) stage. Tomonts need a higher osmotic pressure to finish the reproductive cycle; at a specific gravity of 1.009 they cannot complete their part of the cycle. They die, never to emerge. Whichever the case, hyposalinity works.
Hypo will also kill your inverts such as shrimp, snails, corals as well as live rock and live sand. So make sure you treat your fish in an appropriate area, i.e. in a Quarantine/Hospital tank.
Accurate measurement of salinity is essential to the success of this method. A refractometer is almost a MUST HAVE. I have checked my swing arm hydrometer against my refractometer and the difference is unacceptable. They are pretty close at a level such as 1.025 but nowhere near close at 1.009. If a refractometer is unavailable a floating glass hydrometer will work.
There should be no substrate in the tank during the procedure. A bare bottom tank gives the Tomonts less places to encyst. Also, it will make cleaning a bit easier. A few clean PVC fittings should be used for hiding places for the fish.
Starting with SW at a specific gravity of 1.025 @ 78-82*f, you will want to make a 1/5th total volume water change with clean, aged, treated, FRESH WATER every 12 hours until you reach 1.009. This will take approx 4-5 water changes depending on the volume being changed. Keep a close eye on the salinity during the whole process. Do not lower the specific gravity more than .005 at one time.You will probably see white spots on the fish within the first 7 days of the treatment. The move should be stressful enough to the fish to trigger an outbreak. It takes 3 to 7 days for mature Trophonts (parasitic stage) to exit the fish, with the peak being 3-5 days. Keep an eye on the fish.
The treatment should last 4-6 weeks or for 4 weeks AFTER the last spot was seen on a fish. Again, keep a close eye on ph and specific gravity. Keeping the tank covered helps keep specific gravity in check.
When you are convinced that your fish are Ich free, the salinity should be raised slowly. More so than when you lowered it. Again, treatment should last for 4 weeks AFTER the last spot was seen on a fish.
Raising the salinity should be a done slowly, 3 to 7 days is recommended. Using water of normal salinity (ex1.025) replace 1/6th of the water to raise it from 1.009 to 1.012. As the specific gravity creeps closer to 1.025 you will have to either adjust more water each time or use higher salinity water. When raising the salinity, no water should be discarded. You should raise the salinity of the water removed and then replace the water into the system.
Once you reach your desired specific gravity, you are done. Just reintroduce your fish as if it were the first time they were going into your tank.
I also found it very helpful to keep a daily log of what was happening. It wasn’t much, just a daily entry and a few quick notes.
All fish in the main tank must be treated in order for this process to work. If the main tank is left fish-less during this period, when the fish are reintroduced 6 to 8 weeks later, there will be no Ich in the system.
Most importantly, BE PATIENT.
WARNINGS……………….
It is a dangerous practice to mix copper treatments with hyposalinity treatments. Choose one or the other.
Marine invertebrates will die due to osmotic shock. Sharks and rays may not survive hyposalinity due to their unique method of osmoregulation
If flukes are present, that means a very different treatment from the antibiotics you are currently using. You would use Prazipro to treat flukes, but it is dicey mixing prazi with other meds due to the Oxybispropanol it contains. Only copper seems to be safe to mix it with.
