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Friendly Aquaponics Newsletter
Number 78
April 30th,  2012
Images from our farmily aquaponics farm
Aloha Friend,

Today is the second (newsletter in the series) about the stuff that's plugged our water pump intakes in the past. This seems a mundane subject for an aquaponics newsletter that focuses on technology, but we lost $10,000 once due to a plugged pump intake.

We didn't know what to look for at that time, and were certain it must be lack of nutrients, lack of sunlight, or something we were doing wrong. We'd measured and remeasured everything in the system in question, and were baffled, for it all tested out OK. To find out what it was, you can read our last newsletter in this series, #77.

Inadequate water flow rate can be a serious problem for the commercial aquaponic farmer. Today we'll cover several things that can plug pump intakes or affect water flow rate in your aquaponic system. You can avoid these things without going through the learning curve that we had to. 

If you want to find out how important flow rate is to your aquaponic system, we covered that in our back newsletters #32 and #33, which also include the information we developed on how to scale a system smaller or larger, with formulas and equipment specifications.

If you're interested in learning about our Solar Greenhouse technology, please take a look at our Aquaponic Solar Greenhouse Training (Special Offer in right sidebar of this email), where you will learn more about how to grow affordably using aquaponics in greenhouses than you can anywhere else in the world. The next training is in Hawaii in June 2012. For smaller home backyard and apartment systems, please read on:
Purchase Construction Plans and Operating Info for 4 Different Sizes of Apartment/Condo Aquaponics Systems $49.95

Our Apartment/Condo System package includes new and easy-to-understand building instructions and complete operating information for 4 different sizes of small aquaponic systems based on our years of experience operating a commercial aquaponics farm. Anyone can build a system out of plastic barrels or IBC totes, but operating one successfully without good and easily-understood information can be frustrating. You simply use the "Daily Operations Checklist" in the manual and follow the step-by-step instructions on your way to success. We also cover how to make aquaponics systems out of weird things like old refrigerators and door frames; this makes aquaponics much more economical to get started in!

We spent hundreds of thousands of dollars, hundreds of hours, and built our first commercial aquaponics systems with FAR less information than this manual contains. We included all the information learned from that experience in this manual so you don't need to make any of the same mistakes we did.

Learn about our Apartment/Condo Systems!

Aquaponics Nugget #78:
Pump Intake Filters, Part 2

The Many Faces Of Restricted Flow:

1.  This was a simple one: one day an employee told me there was water overflowing from one of the troughs. I went to inspect, and sure enough there was. Water was coming in from the fish tank, but the fact that it was overflowing the trough meant there was something wrong with the trough outflow, which should have just gone downhill to the sump tank.

We went over to that end of the trough, lifted up a raft of tomato plants that was floating over the outflow, and found a beautiful 3-inch diameter, almost-solid tomato root mass going straight down the outflow standpipe. The tomato had simply dropped its roots right down the pipe until they had grown so big that no water could pass them. Solution? We moved the raft a foot away. Moral? Watch out for tomato plant roots!

2.  This happened in a 64-square-foot Micro System, where the water pump gets its water from the end of the second trough in the system. There was no water coming into the fish tank from the water pump line, even though the water pump was running and there was plenty of water in the trough that fed the pump. There was, however, another tomato plant near that end of the trough, and when I lifted up the raft to inspect the water pump intake filter, I saw tomato roots growing into and through the intake filter.

I removed the pump and found the pump impeller cavity full of roots. The roots had grown straight through the intake filter, through the pipe to the pump, through the pump, and then into the pipe on the opposite side of the pump. This prevented the pump impeller from turning. Again, after cleaning things out, the solution was to get the tomato plants away from the pump intake end of the trough.

filter2Small 2

Here's a typical pump intake filter. This one is shown inside a "mocked-up" trough end; and is the appropriate size (1-1/2" PVC), for our Micro Systems and Family Systems. The little yellow thing is a piece of plastic to hold the filter up so it doesn't knock over the mockup trough end; it's not part of the filter. Next week we'll describe how to make these filters, with pictures.

3.  We noticed about a quarter of the normal water flow in our tilapia nursery system one day, and also noticed that the water level in the sump tank (where the water pump for this system gets its water) was right down below the intake filter. OK, we haven't had much rain, so put the hose in, put in a couple feet of water, and things should be OK, right? Wrong. There was still no flow coming out at the fish tank up top, even when there was 2 feet of solid water over the water intake in the sump tank. What was happening?

The low head, high volume impeller-type pumps that we use with these systems have one Achille's heel: if they suck in any air at all, they lose their prime. This means they will stop pumping, and won't suck in new water by themselves. They simply keep spinning the same batch of bubbles mixed with a little water around and around and around, literally forever. Sometimes they will pump a little water, and sometimes none, when they are in this condition.

The fix for this is to simply turn the pump off for thirty seconds after you have re-established the higher water level required in your tank, then turn the pump back on. When you turn the pump off, all the water bubbles stop spinning around inside the mpeller volute, and percolate up through the pump intake line into the tank, and are then replaced with the solid water that flows down the intake line.

When you turn the pump on again, it is full of solid water and no air bubbles, and will run like this forever, as long as you don't let any air in, or tadpoles, or little tilapia, or tough strands of grass, or 2-inch net pots, or a bunch of plastic plant tags, or plastic bags, or (fill in here whatever has clogged your pump in the past)! To read about proper filter mesh sizing that will keep all this stuff out and still let water through, read our newsletter #77, where we covered that subject.

When you are diagnosing your lack of water flow, a useful test is to sit down near the pump and listen! A pump with no air in it is remarkably quiet; while one with air entrained in the impeller volute is quite noisy! So, as you make the rounds of your aquaponic farm, one of the things you listen for, besides the sound of hissing (which means you have a broken airline somewhere), is the sound of a noisy pump.

4.  Number four is embarrassingly similar to number three, but is subtle and diabolical enough to warrant its own numbered description. Same system, there's plenty of water over the intake, and has been for days, but the pump is making lots of noise! You know what that means, if you have read number three; air in the pump! When we lost our flow again, the first thing I did was to inspect the "pump house", which is the little plywood shelter built over the pump to keep the sun and elements off. I found that it was nice and dry in there, and noisy!

I walk up to the electrical distribution panel in the hatch lab, and turn off the pump. By the time I get back to the pump house, the floor of it is wet, and I can see a drip-drip-drip coming from the flexible tubing that connects the pump intake to the fitting in the side of the tank (got to have a flex coupling here, or you will fatigue a pump part or your PVC pipe, and one or the other will eventually break). What does this mean?

Well, when you have water coming out on the intake side of your pump when it's turned off, that means that air is going in when the pump is turned on. The pump was constantly sucking air in through this little hole that had somehow developed in the tubing. We didn't notice it at first because it only reduced the pump water delivery a little up at the fish tank.

As the hole grew larger (they tend to do that, rather than fix themselves!), the pump efficiency went down and down until finally the pump sucked so much air through this little hole that it didn't pump any water at all! The fix was easy: we just put on a new piece of tubing with no little hole in it.

On a separate occasion, we found that having slightly loose hose clamps on the intake tubing to the water pump produced exactly the same result: air in the pump, a noisy pump, and no water coming out at the fish tank. Again, it was an easy fix.

GrownOut1medium 2

Friendly Aquaponic's FIRST Aquaponic Solar Greenhouse in full bloom, Honoka'a, Hawaii, March 2012, (on a grey rainy day) showing PV panels, growing plants, and the mysterious Verticalis in the center!

Next week: Part 3, Instructions and photos showing how to make these filters (we promised these instructions this week, but ran out of room, sorry!). Thanks for listening!

Click Here To See Our New Aquaponics Video!
Back Issues Of Newsletters Now Available, Click Here!
Purchase Trough Liner Directly From Manufacturer!

Free Farm Tours
Aquaponics tour at the Friendly farm!

We hold a free workshop on our farm the FIRST Saturday of every month,  focused on growing food with aquaponics and permaculture.  Click here for information. See you there!

If you are a school, a non-profit organization, an organization working with the poor, Native Hawaiians, or ex-inmates, or if you are a church, we will hold a free farm tour for you anytime. You DO need to email us first to schedule, or we might be out on errands!


3-1/2 pound kalo (taro root) grown in a 2" net pot (little bump at bottom)


4-month old prawn (macrobrachium rosenbergii) grown in hydroponics troughs of our aquaponics systems

Special Offer! Sign up for our June 27-28th Aquaponic Solar Greenhouse Training, or our June 24-26th Aquaponics Technology Training, and receive a free Micro System DIY package so you can begin studying aquaponics! ($99.95 value)

More Information on Hawaii Aquaponic Solar Greenhouse Training

"In The Farmily"

Every farm has a feed room, feed shed, or feed closet where they keep the different feeds for the various animals on the farm. It is usually a good idea that the animals don't ever have any idea where the stuff comes from, as we recently found out.

It started out simply enough: one of the kids spilled a bit of feed on the ground right outside the feed room while getting some food for the chickens.  The single chicken that we hadn't been able to catch (to clip her wings so she couldn't fly over the fence) found it first.

She told all her friends about the cornucopia over at the house, and pretty soon we had eight or ten chickens who could either fly over the fence, or who found some other way to bypass it. Not long after that, we had twenty chickens at a time waiting for their train right outside the feed room, hoping more grain would get spilled.

This wouldn't have been so bad by itself if we didn't also have goats. We'd had one mother goat and her two babies grazing the grass around the house so we could keep an eye on the babies while they are small, and the mother goat found the feed room.

Now, a goat has considerably more mass and a LOT more leverage than a chicken. When she smelled what was inside the feed room, she simply pried the door open using her head.

So we remembered to close and latch the door next time. Only she had already tasted Paradise, so she simply pried the door off its hinges this time.

We got the long-awaited chicken coop finished, and put all the chickens over the fence with their wings trimmed. The baby goats got big enough to safely go out into the big pasture with the horses, and we put better hinges on the feed room doors.

You heard me mention horses? We've got three Shires, each about 2,000 pounds. Let's hope they don't hear about the feed room from the goats or the chickens, because they can go through anything!

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