Over at aquariacentral one of their users seems to have contacted Lego and they confirmed that Lego is indeed safe… Lego is made of very stable hard plastic and will not breakdown in an aquarium. We don’t recommend you use your LEGO® bricks as decorations in aquariums or fish tanks.Click to see full answer. Similarly, you may ask, is resin safe for fish tanks?Aside from its coating, sealing and moisture-proofing qualities; epoxy resin is completely safe and inert once cured – making it a perfect solution for aquatic areas. A recent article speaks to the versatility and durability of epoxy resin for maritime application including for aquariums.Also Know, are water beads safe for fish tanks? “Non-toxic” doesn’t mean “safe for consumption”. Also, Orbeez might deteriorate in the fish tank water rather quickly, and their slimy surface could be a good substrate for bacteria and germs. Secondly, can you put plastic toys in a fish tank? Many fish shops sell plastic toys, like Nemo or SpongeBob, to include in your tank. When plastics are left in water for long periods of time they can release potentially toxic chemicals into the water, so they should be avoided in fish tanks at all costs. However, avoid one time use plastics such as water bottles.Do Legos float in water?Most Lego bricks are made of ABS plastic which has a specific gravity greater than 1 (but only slightly). So, they are heavier than water and will not float naturally. You can get small bricks to float initially since small bubbles cling to their surface, but they will all sink eventually.