making a aqua bridge aka connecting two fish tank via a fish bridge

[harshy]

hello everybody,
I have seen a few topics about connecting two fish tanks together via an aqua bridge, and after much research, I have concluded to go ahead with building one (an aqua bridge) for the fish to swim though so they could have another environment which they could swim to. (if they are smart enough to realise they can swim though the bridge to another place.)
As certain fish like caves, im planning on hiding the entrances as caves. (to fool the fish so maybe they would swim down it to explore) I will be putting together a plan so if it does work someone else could design or build there own project.
So now you have a rough idea of what im going to do, but as i said earlier I have done my research. But there was one part of information i could not find out, which was do both tanks need have to hold the same volume of water
e.g. two 60gallon tanks---

i want to know if you could have
e.g one 60gallon and one 30 gallon

also if raising one tank slightly high e.g 2-4 inches so one tank could have a land area for maybe a turtle .

I know not alot of people have tried, and many will not beleive it can work. but im guess if i can find the answer here, Im going to have to try trial and error. And NO i will not be trying this on my tank im going to build and experimental setup ive put to much time and effort into my to be testing out things on it and also risk making the fish get stressed

[jsoong]

You can use different size tanks, BUT the water levels have to be the same in both tanks. If you have 2 tanks at different heights, then you can have different water levels relative to the tanks. <But the water level will be the same relative to each other ... or to an outside observer's point of reference.>

Depending on how you filter the tanks, ie if each tank has own filter, vs a flow through setup, there are further limitations on your water levels. <This is in case you lose siphon in the aqua bridge so you won't have a flood & fish on the floor.>

Have you look at the "fishy highway" site yet? They ahve some neat aqua bridge setups.