Tank transfer method
 

Thinking about getting rid of my marine betas ich this way.
Was going to put two snowflakes threw it too . (There just new)

My tanks fish free almost a month (after crash) it was drained and cleaned
So I was just going to take 5 gallons every three days from it and use that water . With a air stone And heater.

If your sure DT is ich free ( which it should be if drained and cleaned) then yes this will work i usually do the last few transfers with DT water helps with acclamation and then the last transfer can just go into the main

That being said some say DT should be fallow for 8 weeks but in your case it was drained so that should reset the timer ( not sure about ich staying on the rocks)

I would also pick up one of those ammonia badges they give you a heads up for ammonia, and grab some prime you can use it without worry

I had ammonia on day 2 of my 20gallon TT tanks (with 2 clowns 2 wrasses) usually every transfer but i did feed heavy cause i wanted them healthy