I just use pvc
elbows and 90's of varying sizes for hiding places. The fish get to hide a bit and I can still see inside. You do need to remove them every few days and clean them.
Vacuuming the bare bottom on a daily basis is essential to remove any tomonts on the bottom along with all detritus that builds up. That should be a 10% PWC
at a minimum. Yes it's a pain, but worth it in the end.
I would not trust the SG
reading until I had a calibrated refractometer. How often are you checking the SG
How are you making up the water lost to evaporation?
That affects the SG
and you have a smaller tank and much smaller range to be kept.
I believe that Hyposalinity is the best method for curing Ich, but it takes time, and dedication to do it right. Remember that the tomont stage of the parasite can be up to 28 days. So not seeing any spots is meaningless unless you haven't seen any for 30 days or more.
The tomont stage is followed by the Theront stage where the newly hatched parasite is looking to attach to a host fish. That usually occurs at night when the fish are resting near the bottom. That stage only lasts about 48 hours. If no host fish is found the parasite will die.
If a host fish is found the parasite is now attached to the fish and growing. This is the only time it is visible. This period only lasts 3 - 7 days before the adult drops off the fish and looks to attach to a surface where it encysts and and grows (tomont stage).
That is why you need 6 - 8 weeks of not seeing any spots AND maintaining SG
at 1.009 (or under 1.010)