Ideas for an classroom fish tank

[FunsizeJav]

Hi all,
I'm setting up 4 10g fishtank in an elementary school. They will go to pre-k, and kindergarten classrooms. I set up bottom with pool filter sand and The background is spray painted sky blue.
My idea is to use magnetic alphabet letters/numbers & silicon on back and on DIY caves/ Lego houses. I will peel off magnets and boil letters before introducing into aquarium. Do I need to take any other measures to keep aquarium safe?
I posted on the wanted discussion board. Accepting donations for 10 g. Setup. A few of them missing hoods, heaters and decorations. That's why doing the whole DIY stuff.
Thanks

[Austy16414]

Ideas for an classroom fish tank

You'll be fine with the plastic numbers and letters, just make sure you let the silicone cure before you submerge in water

[Austy16414]

As far as the Legos, you will either have to drill tiny holes in them so that they don't float, build them underwater so that they trap water instead of air, or build them on a platform that you can submerge in the sand to weigh it down