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vsimo

How much air do I need

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Hi, pulling my hair out trying to work out how much air I need so i can buy a suitable pump for:

7 300mm (1ft) deep tanks running 11 small sponge filters and an airstone in each

3 450mm (18in) deep tanks running 3 outlet undergravel filters and an airstone in each

2 450mm (18in) deep tanks running 4 outlet undergravel filters and an airstone in each.

At the moment I am running 3 tired old Aqua One 9500 air pumps rated 400 to 500 lph and these just do not push out quite enough air and blow diaphragms all the time.

Also if I end up with a pump that blows too much air how do I set up a bleed valve to take the pressure off the pump.

Hope someone can help.

Thanks, Vic

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One litre of air per tank/outlet is fine on shallow tanks like yours. I would calculate and then upsize pump slightly for future expansion.

If you are blowing diaphragms, it's not because your pumps are under powered, it's because they are struggling to push air out (too much back pressure) and it's easier to blow the diaphragm then force air out as you want. I would ditch all your air stones, check valves and use a wide diameter ring circuit to deliver air.

To bleed excess air, just add another air valve that empties into the air, not into a tank. Air will always take the easiest path.

If your dead set on air stones (why?) then use the plastic ones that you can take apart to clean. They have the least back pressure with big bubbles.

Edited by aquaholic99
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One litre of air per tank/outlet is fine on shallow tanks like yours. I would calculate and then upsize pump slightly for future expansion.

If you are blowing diaphragms, it's not because your pumps are under powered, it's because they are struggling to push air out (too much back pressure) and it's easier to blow the diaphragm then force air out as you want. I would ditch all your air stones, check valves and use a wide diameter ring circuit to deliver air.

To bleed excess air, just add another air valve that empties into the air, not into a tank. Air will always take the easiest path.

If your dead set on air stones (why?) then use the plastic ones that you can take apart to clean. They have the least back pressure with big bubbles.

Thanks for the reply,

I am using the airstones because 12 months or so ago I had an outbreak of cyanobacteria and one of the recommended steps to clean it up was to increase oxygen in the affected tanks. I put the long type airstones in each tank and have left them there ever since.

In the past I have just taken a punt on what air pump to use so I asked the question if there was any science to selecting a pump and your answer sorts that out for me.

I am working on one litre for the sponge filters and 2 litres for everything else and come up with a 65 litre pump.

As you suggest i will look at putting in a proper air circuit. At the moment I have miles of non continuous circuit airline hoses and regulate the flow to each tank with a screw up clamp because I have found plastic air taps leak more air than they deliver.

Thanks for the advice I am hot to trot to go and set a a decent air supply.

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Depending on the type of air stone, you can unclog and revive them with fine sandpaper but apart from slightly more surface area (smaller bubbles), the tank water turn over can still be matched with coarse bubbles and even no air stones. A small power head or pipe to make air uplift will improve tank turn over further. Tank turnover being the key to increasing dissolved oxygen levels.

I'm pretty frugal but I'd expect to run 100 outlets with a 65 LPH air pump. I've been known to put airline only half way down the undergravel lifts and dislike air stones though.

If you do opt for a central air circuit and can afford it, two smaller sized air pumps on the same circuit provides better safety than one large air pump. All pumps will eventually fail. If one small pump fails, you will immediately notice but the other pump will continue until you repair. This is only of importance if you have high stocking rates or expensive/sentimental livestock. I place each pump on different electrical circuits and have one circuit on automated backup power supply. However I run quite a few tanks so it's worth my while to do so.

You might want to consider 4mm micro irrigation taps for your air valves but clamps can work well too.

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Even though it may be a little more expensive, It's a good idea to have back-up parts or a back up pump.

I actually purchased 2 x airpumps when setting up my centralised air system for my tanks. One has never been used, and is for backup only.

If the main air pump fails, it's simply a mater of unhooking it and hooking up the backup pump.

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Even though it may be a little more expensive, It's a good idea to have back-up parts or a back up pump.

I actually purchased 2 x airpumps when setting up my centralised air system for my tanks. One has never been used, and is for backup only.

If the main air pump fails, it's simply a mater of unhooking it and hooking up the backup pump.

Good advice. Try to get all air pumps the same brand/model to reduce spare parts. Also advisable to turn your spare pump on once a year just to make sure it still functions.

I used to do this about 3 fish room versions ago but now prefer to have two smaller pumps running on the same air circuit as this gives real time backup. When one pump fails, the other pump continues to supply air at a reduced rate (it's immediately noticable). This is better than having two air pumps on two separate air circuits and two lots of air stones/filters in each tank. The next step after that is to back up your power so air continues even during power outages.

Or the most fail safe method is to have a low stocking rate. No need to do anything at all.

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