Currents in a fish tank
It is important to always get proper currents in a fish tank. Without them serious problems can arise for the fish. They might not have enough flow to work against and stay in shape, or there may be too much and the fish are blown all over the aquarium. In a blog post called Which Direction Should My Fish Tank Filter Outlet Be Pointing on www.tropicalfishsite.com the comment is made:
Something which often gets overlooked by filter and aquarium manufacturers is the finer details on how things should be set up. There is no right or wrong answer to the question of which direction your filter outlet should point however I would strongly advise that the best direction to point it in initially will be towards the surface of the water.
I do agree that the water surface should be agitated so that surface tension is broken and carbon dioxide can be released while oxygen is replenished as much as possible. Water carries much less oxygen in it, so the more oxygen avail;able the more comfortable the fish will be.
Currents in a Fish Tank do Other Things
When deciding how to set up currents in a fish tank, the output of the filter should be considered. When you have a standard clip-on filter like an AquaClear, there isn’t much you can do to control the way the currents are produced. The waterfall effect does drive some air into the outflow and the water is mixed in a rolling motion from the top to the bottom. This can drive the fish to the bottom and may injure small ones if they contact the substrate.
Canister filters, and other pumps that direct the flow better should be placed so that the currents in a fish tank are as lateral as possible with the direction in as long a run as possible. Try to make the currents in a fish tank run the length of the aquarium and then around the corners. This is much better for the fish than sending the water flow from the back directly toward the front glass.
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