Hello Jonette,
welcome here.
Always and everywhere there is place for one, two or three additional tanks 😉
On the picture you see my last extension.
A shelf, ca. 25 – 30 €, bought in a construction market.
Ok, for a living room it isnt the hit, but an aquarist must set priorities 🙂
I cant help with Eichenextrakt – i use peat.
Greetings Arno