Haha, I do also have a cycled HOB filter I can use! I also have two or three uncycled internal filters for that matter... was thinking of switching to or just adding an internal to the oto tank since they like a bit of current.A HOB filter sounds good to me at this point!!
Only kidding, well, the sponge filter tbh is the best filter for shrimps and snail tank set ups. But they'll be fine with whichever filter you decide to use for that tank.
A case of trying things out and moving the filters in different positions to see which outcome you like the best, you wont know until you try.
The shrimps will be fine with you moving things around in the tank, in fact they'll probably like it because you'll be stirring up new foods for them to munch on
The plants are starting to look good. Too early I think to know for certain if they'll do well or not but looks like a good start anyhow.
Dragonstones look cool, and shrimps DO like them due to the hidey holes and a sort of adventure ground for them to climb around on.
I was planning a direct swap of the canister for the double sponge mainly because both are fully cycled. I've ridden out a mini cycle in the guppy/shrimp tank since it was so new and clean even with the established filter, and now riding out a mini cycle in the quarantine 12 gallon that has four baby cories in it, so wasn't keen on riding out a third mini cycle in a row. Plus the internal filters are surprisingly powerful for cheap internal ones, too much flow for guppies, and risk of sucking up fry and shrimplets.
But! There's another alternative. I could switch the canister filter AND the single sponge filter from the quarantine tank to the guppy/shrimp tank. Best of both worlds! Takes up much less room than the double sponge, but shrimp will still have a sponge, and canister can do the heavy lifting while plants are still growing in.
Or the HOB can come into play...
Decision, decisions! Help! lol