I turned 54 a few months after I set up my first tank. I quickly progressed to multiple tanks which usually meant a smaller tank on the bottom shelf of a stand. I used to call them belly tanks because I had to lie flat on the floor on my stomach to watch the fish for any length of time. To work on such tanks I had to sit cross legged on the floor.
It did not take many years for age to catch up with me. I found it very hard to get up after sitting that way for 15 or 20 minutes. This led to my insisting any under tanks must have it's bottom at least 12 inches above the floor. This also made vacuuming a lot easier. I would raise stands using stacked 4x4s joined together with metal plates and screws or a 2x6 frame. See the two stands on the left in the pic below.

(The middle stand can hold a 36x18 tank over and under, the other two stand must hold a smaller size tank on the lower level.
I have a wheeled step stool with spring on the wheels. Stand or sit on it and the weight causes it to lower ont to the flor and not move. I sit on it when I work on under tanks.
This has an interestng side effect I enjoy. In most cases when I sit on the stool to work on the under tank I am also at eye level for the bottom of the tank above. I only stack 2 tanks on my stands. I have been able to watch some things I might never have seen sitting on the stool.
I once watched a male L236 who had grown quite a bit for the small cave he had claimed. he had convinced a female to spawn with him but when she went into the cave he could not fit. So the gal was willing but he was not able in his current cave. However, it is my practice to put a number of caves of different shapes and sizes into pleco breeding tanks and let them figure it out. He fit fine with room to spare when he first "leased" the space.
As luck would have it about 4 inches to the left of his cave was a bigger cave which was unclaimed. The challenge was how was he going convince the lady to abandon the cave she went into and go into the adjacent cave. More importantly, would he figure out his salvation was so close by.
During all of this I was working on the tank underneath which held another spawning group. So I was mostly paying attention to that. But when I was done and ready to move onto the next tank I noticed the pair was now together in the bigger cave. This whole thing was at eye level whenever I sat straight up on the stool.