@Vincerama2 you are right, I also used the hyposalinity treatment against ich successfully in the past.
Yes, I had to catch all fish, including the ones that show no ich signs and move them to a QT. There are various ways to setup the QTs, most recommend not to use rocks & sand. AFAK, that is because of few reasons:
- medications usually attach to rocks and sand, so the soluble percentages change & dosing becomes tricky. For example copper will attach to rocks and sand, then slowly leak back in the water, so if one would use copper to treat ich it will have to dose more initially, but then the copper leak from rock/sand could bump the concentration over the safe levels.
- rocks & sand are a very good medium for bacteria and critters, but the fish medications or hyposalinity are very likely to kill those, so the result is a high level of decomposing organics which means a surge in toxins
- some believe that parasites such as ich need rocks & sand to attach during their life cycle when they multiply
In my case the QT was a 30G tank with an overflow and a 20G sump. The equipment consisted of return pump, heater & ATO. I also had a skimmer on hand, but it is useless when doing hyposalinity, because the air mix with low-salt water doesn't produce the needed bubbles to pull out the nutrients.
I had a think layer of sand in the sump, it was a freshly rinsed sand, not a "live" one. In my case the sand became "live" with bacteria that formed during hyposalinity, and it helped with the nitrogen cycle throughout the treatment.
I followed the process explained by Leeb on various forums such as this one:
http://reefsanctuary.com/forum/index.php?threads/a-hyposalinity-treatment-process.23131/
I lowered the salinity to 1.008-1.009. The ATO was critical in this process: it helped me keep the salinity low & it also served as the perfect way to slowly dose baking soda to keep the pH swings in check.
I kept the fish in low salinity for 1 month.
The recommended time to keep the tank free of fish is at least 2 months. That actually matches the hyposalinity treatment timeline, which in my case was 2-3 days to lower salinity from 1.025 to 1.008, 1 month at 1.008, then 2-3 weeks to slowly bring the salinity back to 1.0.25 & monitor the fish (the way down to 1.008 can be pretty fast, but the way back to 1.025 has to be very slow).
The hyposalinity works because the marine ich can't survive in low salinity water as most inverts cannot either. Also 1.008 is considered the lowest limit for fish so it is a bit dangerous
.
While the ich is attached to the fish, it is safe in its shield. Once the ich reaches maturity, it has to detach to complete the multiplication process. That's when it swims in the water to find a place where to attach and shield again. While it swims it is vulnerable and is cannot survive long in low salinity water.
There is also a "good" side effect of hyposalinity: all my fish got super fat - imagine the tangs getting obviously rounded !
I did some reading on it, I say it's from 2 combined reasons:
1. I fed the fish more while they were in QT so they can fight the disease better
2. Low salinity water means the fish need less energy for their metabolism, so they burn less fat & calories
