Why are Air Pumps rated 'Up to'?

Rocketman

Rocketman

Detroit; proud of it.
Oct 24, 2002
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Hey. I am purchasing a Rena Air Pump and trying to decide whether I should go with the #200 ($25.99) or #300 ($36.99) model. The #200 pump says, 'up to 30 US Gallons,' and the #300 says, 'Up to 75 US Gallons.' Being as this is a 60 Gallon tank, the logical choice would be the #300. But since the air pump is not pumping water, I was wondering why there is any capacity rating. If the #200 puts out less air, this would be a plus as this will be a mildly planted tank.

Any thoughts? Also, if you have heard any bad things about these brands, speak up please. Also, those prices are from Bigals.
 
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Interesting question!!

I would guess that the ratings are based on how much air it takes to drive UGF's of varing sizes. It seems like a very "hit & Miss" formula.

So basically, if you are driving 4 uplift tubes, you want the bigger pump. If driving 2, the smaller would do.


Geez!!! It has been along time since I have messed with uplift tubes. It seems like a lifetime ago.
 
Hey, thanks for the reply. No UGF system, just pumping free air through an air stone for aeration. But from your reply, I assume the #200 will do. It saves me like $9 so its worth it.
 
Heaters:
The reason for 2 smaller heaters vs. 1 large heater is for redundency. If one heater goes out(not heating) the other can take up the slack until the broken one is replaced. Also, If a large heater sticks in the "ON" position. Your tank will heat up much more and much faster than if one of the smaller heaters sticks in the "ON" position. The Ebo-Jager is the best choice IMO. If you choose to have only one heater, this is the brand to go with. It is a very tough and reliable unit. (It looks slick too)

Gang Valve:

Penn Plax makes a decent one. I have used the 3way and 5way valves from them and never had a problem. I did notice that the valves are not very sensitive. I would prefer a bit more control than what that unit gave me.

Filter Media:

Ehfisubstrat is the Bio-media provided with Eheim canisters. You want this for sure. I did not use all the media that came with my 2028 because I have a planted tank. Chemical fitering tends to remove fertilizers. I did use the Ehfisubstrat, the foam pads(not carbon ones) and the EHFI-Mech ceramic rings.

That is one great filter. You will love it.
 
One last thing. Do the pipes to direct the water flow come with the filter? I assume the hoses do, anything else I need
 
i'm confused at a few of the answers posted.....

the answer to your basic question tho, is the pumps are rated for a reason that hasn't been mentioned yet. pressure. it takes more pressure from the basic pump to drive the air further down a small restrictive tube, especially when you submerge it. the bigger the pump and higher rating, the more tubing and deeper into the water it is expected to have to deal with, so it requires more pressure.

if you bought say the smallest pump, and put it in deep water, even with a small airstone you might not like the results.

good luck
 
That was my first thought as well ewok. Then I realized that a 35 gallon and a 65 gallon tank are both the same depth namely 18 inches. Having said that I would have thought it would be far more helpful if the pumps were rated for their number of outputs and depth to which it is suitable for. That information would make for better then ranking because of tank size.
 
Thats just what I thought too! It must be PSI or something like that, but consider this. If you place an air line at the bottom of a 35 gallon tank that is say, 18 inches tall, there is still less pressure pushing at it from the sides then there would be if it were placed at the bottom of a 100 gallon tank which was also 18 inches tall. Now, granted those towo measurments aren't likely, but its the princible that matters. But, would a #200 work? Like I said, I would prefer a low output as I want this tank as quiet as possible, and it will be planted.
 
Pressure would only matter in the downward direction. You would have the same preasure in a vessel 5 inches across or five feet across so long as the depth is the same and they are at the same feet above sea level. PSI is a measurement in this case of resistance and it would matter little how much water we are talking but only how deep the water is.
 
sort of vaguely disagree on theory or principle darkangel..... if that was the case then my 55 and 90 should be made of the same thickness glass.... maybe i'm overtired, but water pressure is water pressure, it's not measured just by depth, i think weight has to figure into this too..............
 
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