This is not expert advice from any standpoint so maybe someone can affirm this would work. But I have a tiny 2.5 tank for a baby betta. Cleaning gravel is impossible with regular cleaners.
I found a you tube video and copied the diy cleaner. It was made with a regular size water bottle. It does not remove water. It was designed for larger tanks so I had to reduce the size by finding a slimmer smaller container. I'm new so I can't link or show pictures.
1) I took a slim plastic container, cut the bottom off, (one that will fit between your plants, rocks, wood etc)
2) used a couple rubber bands to attach a small (maybe 5") section of panty hose foot on the end where the cap went ( I ended up putting a piece of poly batting inside to catch tiny stuff that would fly out of the panty hose, it worked)
3) on the cut end, about a half inch up I punched a hole in the side and put a small round air stone inside with the nozzle sticking out the side of the container
4) I attached an air pump via a standard clear hose.
5) maybe not nessasary, not in the instructions, but have a valve that controls the airstone bubbles so I can slow the suction
When you put it in the tank, turn on the air pump, the valve will help how much force is sucked through the container so you can go slow and take your fime without loosing water or sucking up your substrate. The batting also helps slow the suction.
I was able to clean my 2.5 and 5 gallon tank this way without clouding the water too much. Of course I change my water when nessasary but I'm so slow at cleaning the gravel I would completely empty the tank if I tried even the smallest tank cleaner.
If this is bad advice someone chime in please. Is there an easier way to clean nano tanks?
All it cost me was a pair of pantyhose. Everything else was laying around anyway.