Need help designing off grid koi pond circulation system.

Narnian

Hello! My first post on this forum.

I built a small Koi pond in the far corner of my yard about a year ago. To keep the fish and plants healthy it needs to have a pump moving the water through a filtration system 24/7 with a minimum flow of 1200 GPH (gallons per hour). I've been using a 2000 GPH pump with 150' of extension cables. If I remember correctly, when I hooked it up to my watt meter it was pulling 235 watts (110AC), so I think it would be inefficient to use it with a solar power source.

I want to get rid of the extension cables and put in a very small off grid solar system. To do this I think I need to use 12V pumps. I've tracked down a pair of 12V pumps that I can purchase which would meet the volume requirements when used in parallel. 12V pumps means I don't need to buy an inverter. But I'm not confident about how many panels and batteries I need to be successful.

There are two 12V pumps I'm looking at. The first one is really inexpensive at $49 each. You can run it as 12V or 24V:

Power consumption 5.0W@12V	Output 240GPH
Power consumption 21.5W@24V	Output 410GPH

I can run 3 of these at 24V to get 1230GPH flow ($150)
I can run 5 of these at 12V to get 1200GPH flow . ($250)
12V means two golf cart batteries ($170) or one deep cell ($90)
24V means a minimum of 4 golf cart batteries ($340) or two 2 Deep Cell Marine batteries ($180)

It looks like 5 pumps and one deep cell is my best option. But . . .
First question: Would one 100W solar panel be enough power?
Second question: Would 1 deep cell battery be OK in this application or would I need two golf cart batteries?

The second pump is more efficient but also more expensive at $150 each. You can run it at 12V or 18V:

Power consumption 17W@12V	660GPh
Power consumption 33W@18V	898GPH

I can run 2 of these at 12V ($300) to get my minimum 1320GPHflow.
I can run 2 of these at 18V ($300) to get a better 1796GPH flow.
12V means two golf cart batteries ($170) or one deep cell ($90) but I'm not sure if that's enough juice.
18V means I have to buy three 6V golf cart batteries ($255).

Third question: How on earth do you charge three 6V batteries with a 12V solar panel?

Fourth question: would 1 solar panel be sufficient for both of these setups or would I need more?

I'm in Sacramento CA where we get a LOT of sun. In the winter we get some cloudy and rainy days but filtration is less critical in the winter as the fish are not very active when it's cold. If the pumps are running 18 hours a day in the winter I think the fish would be OK. The rest of the year it must be 24/7.
I intend to buy a charge controller to keep from frying the battery.

mike95490

12V brushless pumps would be ok.  But if the pumps use brushes, pass, they will wear out, and need frequent replacement.
What is the reliability requirement of the system?  What if it fails?  How long before the fish start to die ?  What happens now if there is a power outage and the pumps stop ?

I'd really look into installing conduit and pulling wires.  Maybe install a UPS.   But the failure rate for first time installs, unless it's overbuilt, is high.   Do you ever get 3 days of cloudy weather in the winter ? Panels under clouds produce nearly nothing, I get 10% or less, of nameplate on cloudy days.