Increasing Usable Space?

I recently cleaned out my leos' cages, and it seems that my geckos are gettign more active. I have one in a ten gallon, and a 20gL. I have my smallest gecko in my 10g tank. He is seeming to be the most active, so I was wondering if there was any way I could increase his space without getting a bigger tank? He's small, still growing, and once he's bigger he will be joining my other two geckos in the larger tank.

What are ways I can increase his space, maybe adding another level, so he has more space to roam? Are there hides I can get that would help with that?

Also, where do you buy your tank accessories? +++++ is extremely expensive, so I try not to buy from them, but they are the only pet store around here that really sells them. And can you use fish tank accessories? (Obviously cleaned ones or new ones)

Thanks!

If you get some silicone, it is quite easy to mount various objects to the glass, creating ledges for them to climb on. That is personally one of my favorites to do.

Another alternative is getting some kitchen tile, and using smaller tile to hold it up (silicone the smaller tiles to the larger, to eliminate any risk of it falling) and it will double as both a hide below, and an extra level on the top

Thank you, but may I ask what you mean by silicone? I'm not sure I've seen it used for that, mostly just rubbery items like some cups, cupcake molds etc. Also, where would you buy this silicone?