Water flow dynamics

[Dupe]

I know next to nothing about flow dynamics in an aquarium. Are there any "formulas" and/or schematics of design for proper water movement in the discus environment? For a starting point consider a 75g tank which is what I have but a general description including equipment choices and how to best manipulate them would be appreciated for any size tank. Thanks in advance.

[DR.V]

Discus prefer calm water ... So not too much of water movement in the tank.

HTH

[Merrilyn]

Welcome to the forum Dupe. Can't offer you much in the way of a scientific explanation, but if you can put up with my 'layman's' terms, I'll try to help you.

The idea is to create a gentle 'rolling' effect in the tank, so that the water is moved in a circular motion around the tank.

If, for instance, you were to use a canister filter, the water intake and the spray bar can be at the same end of the tank. The spray bar (or normal water outlet) would be directed to the far end of the tank causing the water to move in a circular movement and bringing stale water back to the intake pipe, where it would be filtered and returned to the tank.

I'd suggest you fill your tank, and add your filtering device but nothing else. A few drops of food colouring in the water will clearly show you the swirl pattern. Try again but this time add your pieces of driftwood and any tank ornaments, and once again add the few drops of food colouring.

If the dynamics of the flow have altered, you may want to reposition your outlet or intake, till you achieve that gentle roll.

Discus come from very clean water, and have a high oxygen requirement, so I use airstones in all my discus tanks. If you position an airstone near the intake (but not so close that it draws in bubbles) it will also help to draw water towards the intake, where it can be filtered. Oxygen exchange can only take place at the surface of the water, so drawing stale water from the bottom of the tank up to the surface, allows the gases to exchange releasing carbon dioxide and allowing oxygen to enter.

Hope that goes some way to answering your questions. :P