Lots of uses for the tube idea. You could put a grillover both ends of the tube to prevent fish entering the tube, and have it so that both tanks share the same filter and heater, but two tanks, which mean that each tank will have less equipment in it, if one has the heater and one has the filter, also it will make water changes easier as it will only have to be done on one tank instead of two seperate ones. It may be nescissary to gravel vac them both, but its better than doing two WCs.
Also, if keeping more aggressive fish, it can allow a bullied fish or a fish being picked on to change tank via the tube and therefore escape the aggression.
I think its a great idea with many uses, or even if you wanted it to just be a cool looking tank(s).
Lots of uses for the tube idea. You could put a grillover both ends of the tube to prevent fish entering the tube, and have it so that both tanks share the same filter and heater,
Would you not need two filters and heaters- I'd suspect water flow between the two would not be optimal and you'd get the water in one cycling more than the water in the other (obviously there would be some flow between the two) - I'm not sure the heat would be even either.
You'd have to have the filter intake on one side and the output on the other. A lot of fish like to swim in current, so I'd imagine there would be fish in the tube a lot. Also, I'd attach them permanently to a solid base to keep them from moving as the connection would probably be pretty weak. BTW, I had a tank like this, when I was pretty young, I'm not sure if it even had a filter actually, and I have no idea what was in it, just that it was pretty small, probably 10gal or less.
glass-holes.com has everything you need for drilling tanks. Just confirm that the glass is not tempered before you try and drill it. Also, use bulkhead fittings on the holes to connect the pipe...much more solid than just trying to silicone a pipe in a through-hole. A canister with intake on one tank and output on the other would ensure good flow through both tanks. I did this idea once before, but it was with rubbermaid tubs, not glass tanks, so slightly easier.