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Comment by TCLynx on February 22, 2012 at 10:47am

Well there is an Off grid group that might be able to help you figure more out about trying to do solar aquaponics.

Off Grid Group

Bob, the bigger pump might almost provide the flow you need at 0 head under perfect sun conditions and perfect battery conditions.  However, you are not pumping at 0 head so that bigger pump may or may not prove sufficient.  If you try it, make sure to keep your fish load very minimal.

Comment by Bob Vento on February 22, 2012 at 10:20am

Does anyone use a 12 volt marine submersible bilge pump for their system? They have a 1500 GPH for about $90. Any thoughts on this 12volt DC 4.8 amp bilge pump on a battery with solar charger?

Comment by Bob Vento on February 22, 2012 at 10:05am

Awesome info everyone and I really appreciate it.

I do have an issue with electricity in the location where I plan to put my system, so that is why I was opting for a solar solution. However, after receiving all of the wonderful advice, I guess I will have to consider going with an AC pump instead of a DC one. Will have to consult an electrician and factor in that cost. Whew!

I thought that the other pump model I linked to  http://www.esolarlighting.com/8W-Solar-Powered-Water-Pump-With-Batt... ,
might do the trick since it had a higher flow rate and better lift capacity but no one commented on it at all?

Comment by David Owens on February 22, 2012 at 9:32am

I have followed TCLynx advice and always installed larger pumps then I needed. This proved to be cost effective in the long run as we all seem to catch the AP bug and upgrade systems or add grow beds. Another great thing to look at is energy usage. Sometimes the larger pumps I bought used less energy saving me money and allowing me to add solar power easier and cheaper in the future

Comment by TCLynx on February 22, 2012 at 9:17am

Bob, the 2 gpm is the recommendation for minimum flow through a raft bed, not necessarily the minimum flow for the filtration of water for a 200 + gallon fish tank with a media bed.

To pump your 200 gallons of fish tank each hour, you need at least 3.33 gpm at whatever height you are pumping to.  So say the surface of the water (at the low water level) in the fish tank is 2.5 feet below the highest point you pump to then you want to find a pump that will deliver at least 3.33 gpm at 2.5 feet and in general it is better to have more flow rather than less.  You can often eek more flow out of smaller pumps if you upsize plumbing and minimize the length and number of fittings but that will usually only reduce the friction loss, it won't make the pump lift more water higher.

That solar pump might manage 2 gallons per minute but only at 0 head.  It will NOT pump 2 gpm if you are expecting it to lift the water up to a grow bed draining back into the fish tank.  Now perhaps if you were to run 3 or 4 of those pumps you might manage it but at that point it might be easier to get a single regular pump that can do it for under 40 watts and probably under $50 for the pump.

Comment by Sheri Schmeckpeper on February 22, 2012 at 9:03am

Bob, you have to look at two numbers on the pumps. The gph is max flowthrough, but it doesn't account for gravity. The lift is the max it will raise water...any water...not the total gallons promised. So the higher the lift, the lower the gallons it can pump.

We're currently running a 258 gph with a 6'4" lift, and it's doing the job in a tote 1' shorter than yours, lifting about 4'. It's doing the job, though in the ideal world we'd have it a little larger. You'll be lifting at least a foot higher than this. So while you might get away with one the size of ours, your circulation won't be optimal. The added investment will be worth the gain.

Comment by Dave & Yvonne Story on February 22, 2012 at 9:00am

Rated flow rate is based on no lift and no friction.

Most pumps will give you a flow rate at heights about the pump, too.

Comment by Bob Vento on February 22, 2012 at 8:46am

Cost is also an issue with a solar system. The linked one was very reasonable. I read someplace that 2 gallons per minute was a good flow rate, is that not correct? That would be 120 gallons per hour and that pump has a flow rate of 132.09 gallons per hour. This is my confusion do you think this model would work ...
http://www.esolarlighting.com/8W-Solar-Powered-Water-Pump-With-Batt...

Comment by Jon Parr on February 22, 2012 at 8:22am

I agree Bob, pump too small to be used by itself. You could use it for aeration, and configure another pump to operate a flood and drain cycle, maybe come on 10 minutes every couple of hours to fill the GB's. Solar certainly feasible, just not that simple.

Comment by Bob Vento on February 22, 2012 at 7:59am

So even at a 24/7 flow this is will not work? That is a shame ...guess I will have to rethink this. I really wanted to be off the electric grid for this project.

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