Backyard Aquaponics
A place to discuss aquaponics

Sooooo... We are in the middle of a power cut.

I've looked at UPS before but never buy the bullet to buy one.

I think it's time.

What size UPS would I need to run my pump for a good few hours/day or so?

My pump is a Jebao 6,500 lph

Hard to say... stick it on an energy meter and see how much power the pump consumes continuously/ energy over the period you wish to cover.
Are you wanting to run an air pump too?

I have an air pump but I was more concerned about the water pump. In a blackout situation is it better to just run an air pump?

Oxygen for the fish is more important than water for the plants. If you have say 30 trout in the tank, they will probably survive 8 hours with no water circulation, but probably not 8 hours with no air, depending somewhat on size of fish and water temp etc.

This topic gets knocked around a bit and I'm not sure what's right. If you run the water and there are plenty of drops in height or you spray it across the surface wouldn't that satisfy the oxygen requirements as well? I never have run an air pump on the AP system but I have on the filters in the RAS

Exactly what my thinking was. Heaps of people run AP systems without air pumps. And I will not be overstocking my system so the air pump is just gravy...

Depends somewhat on what fish you have. Trout have a higher DO demand than most other species. An air pump, whilst it may generally be a redundant accessory if lightly stocked, is good insurance against pump failure, and if relying on a battery backup power supply, will typically keep going a lot longer than a water pump due to its lower energy use.

Ok so my air pump is a 38L/min 18W Electromagnetic air pump.

I'm avoiding the expense (and the power wastage) of a UPS by using a Hailea DC air pump and a 12V battery. For the same cost you'll get longer backup duration, without the cost of the UPS, and the DC air pump is less expensive than a decent UPS. By using a pressure switch from a washing machine to operate the backup, I protect against power failure and also air pump failure.
If you are using the water pump full time, you could use a pressure switch on the outlet to turn on a DC water pump in the event of power or pump failure too .

Thanks Gunagulla! I just looked on eBay and there's so much variety I am even more confused.

What brand are the ones you bought?

I've got a 25W Hailea, I think it's 55lpm, and a 150AH battery, which would run it for well over 2 days if it wasnt getting any solar charging. Switching is done with an old washing machine pressure switch, you should be able to pick one up for free from a washine machine repair shop.

Gunagulla, can you explain how the float switch activates the 12V backup?

+1 on that ^.

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I have my main 230V air pump pumping ~60lpm running full time, through 2 air discs ~50cm under the surface in the FT. In between the pump and the FT is a muffler to reduce the vibration transmitted into the FT, and I have a brass fitting in the end cap of that, running a length of clear PVC pipe to the washing machine pressure switch, which has Common, NO and NC connections. I have the NC connection in series with the positive wire to the 12V Hailea kept open by air pressure, so that when the main pump is turned off the switch closes the contacts and turns on the 12V pump. The air discs close off and seal in pressure, so I have a few pinholes in the connection to the pressure switch for a slow air bleed, an insignificant volume so it has no effect on the operation of the air discs, but it ensures the switch triggers within a minute, rather than after many minutes. With air stones you wouldn't need to worry about that.
The 12V Hailea delivers air to a single larger air disc placed near the other 2, via independent piping. All air delivery pipe is 25 or 19mm, for minimal frictional resistance.

Google 'ups car battery'