Can You Use Bonsai Trees for A Regular Fresh Water Aquariums?
Bonsai trees are just regular trees pruned down over the years- any tree can be a bonsai tree.
Your best bet is finding some driftwood that looks like a tree, and tying in moss to make it look like leaves. Moss is easy to care for, low light, so shouldn't be too hard.
There are no trees that will grow underwater for very long before dying, unless you count mangroves and other trees that are semi-aquatic and even they hate being fully submersed too long.
I've seen some stunning moss trees that have used dead bonsai stumps (aged for an appropriate amount of time) - maybe call your local plant outlets, see if they have any old dead ones you can have. Might have to wait 2 years for the wood to age, but wow - they look amazing in a tank.
How Tow Make Aquarium Trees Video
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