Oh okay so small fish, you can use bins from like Walmart it’s cheap, you need 2 bins, 2filters, 2 heaters. You want to be sure you don’t cross contaminate so don’t put the 2 tubs next to each other encase you splash water or any other reason. You also want to bet the fish and try not to put any water from the dirty tank into the clean tank(try to just let the fish jump into the new tank or nicely drop it in. I place a tower down so I can place the new for a second to catch the dripping water. I normally use the water from my DT to fill the transfer tubs but you have ich so you can’t so that, just make sure you acclimate them to go into the transfer tank the first time. After that you should have the same water chemistry from the mixed water then when you get ready to put them back you need to acclimate them to go back into the DT(after you treated the ich)