Looks like normal weathered wood that you find near creeks, and rivers.... Best thing would be the fingernail test.... It's where you poke the wood and see how easy it is to sink your fingernail into the wood, if you leave a fingernail imprint that is somewhat "deep" then it's likely soft wood and should not go into an aquarium, but if it's hard wood where you can't sink a fingernail into the wood but only leave a slight mark then it's fine for aquarium use.