Canister Filter Questions

[landrover60]

I have a 55 gallon tank with a Penn Plax 700 cascade filter with the spray bar running. In the tank I have a single 5" Jack Dempsey (my "pet"). I have had this set-up for the last 6 months or so. I have always pointed the spray bar down so it does not create any bubbles in the tank. I am wondering if this is correct? When I clean the filter or do a water change and the water level drops creating a lot of bubble turbulence "he" seems to be more "happy", i.e. he is more active. I am wondering if it is better to have the turbulence/bubble condition constant. My original thinking was that they are supposedly still water fish and do not like the turbulence/bubbles in the tank but his "mood" seems to be better. Any advice would be much appreciated. I have never had a canister filter before so this is somewhat new to me.
Thanks!!
Don
landrover60

[d_frag]

In my experience with spray bars the function is to create a form of current. If the spray bar is pointed in an upward it is also creating surface turbulence which aids in the O/CO2 exchange. You did not indicate if you also have a bubbler in the tank, so an assumption could be made that the oxygen levels in the tank are depleted since there isn't enough agitation at the surface. Also, if the spray is pointed down, it is creating a sub surface current that your JD may not find appealing.

[Narwhal72]

Canister filters are very good biological filters which means that the bacteria inside them will strip the dissolved oxygen out of the water. When the spray bar is pointing down this pushes this low oxygen water to the bottom the aquarium and reduces the dissolved oxygen in the aquarium. It's better to shoot the water across the surface so that this low oxygen water can exchange gases with the atmosphere and reoxygenate itself.

Andy

[chc]

What they said...... PLUS:

Don't worry about too much current. Even fish that aren't from fast moving waters rarely see current too strong for their liking in an aquarium. What looks to be fast in a tank usually doesn't even come close to match the current of even a small stream. Most of out filter outputs shoot water linearly in a tight pattern (a spray bar does the same, just with more individual currents). Such water patterns do little to stir the entirety of the tank, and even if they did there's usually no harm.

[smitty]

I have my spary bars spraying across, but I do not think this create any more oxygen exchange. I have always been under the impression that as long as water moves regardless of the surface bubbles you will have the exchange.

[chc]

I have my spary bars spraying across, but I do not think this create any more oxygen exchange. I have always been under the impression that as long as water moves regardless of the surface bubbles you will have the exchange.

It is true to say that bubbles don't equate to better O2 exchange than do no bubbles (apologies to my old English teacher for that sentence!).

As long as you have strong water movement you're fine. The goal is to circulate the entirety of the tanks volume in a manner that allows it to contact the maximum amount of air, and there are tons of ways to do it.

That said, a strong powerhead produces no bubbles but terrific oxygenation. Conversely, an airstone can produce a great deal of bubbles without approaching the oxygenation capability of the powerhead. Every situation is different -- very strong air flow can produce lots of water movement and weak powerheads do little at all.

Simply put, though, as long as you have a good deal of surface agitation you're generally fine.

[Narwhal72]

I think you guys are missing the point. We are specifically talking about the water exiting the canister filter. Which will be much lower in oxygen than the rest of the aquarium. Since gas exchange can only occur at the surface it is better to get this low oxygen water spread across the surface where it can exchange gases. Then the average oxygen levels of the aquarium will be elevated.

If the low oxygen water from the canister is directed down into the aquarium it cannot exchange gasses until it circulates itself back to the surface. This can be seconds or minutes depending on the current in the aquarium. It could be even worse if there is a film on the surface preventing gas exchange. The end result is that the average oxygen level in the aquarium is lower than what it could be.

Getting the water to the surface and breaking up the surface tension with turbulence (powerhead, airstone, filter discharge, etc...) are the best ways to keep the water oxygenated.


Andy

[chc]

You are correct. The "seconds to minutes" part is a key point.