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Comment by Bob Campbell on March 3, 2012 at 9:39am

Holly, I made this video of a no hole aquarium overflow that I use on my fingerling tank.  The advantages of the sump are that it's easy to add water to your tank with less worry about temperature matching and it creates a buffer so that as evaporation occurs the level in your fish tank remains the same.

This over the top overflow is simple genius.  Here's a link to help you build one..

I have added an extra leg to suck the poop off the bottom and avoid loosing floating food to the sump.  .  

Comment by Bob Campbell on March 3, 2012 at 8:27am

finding some of my own answers: pump animation: http://www.ecofilms.com.au/2010/06/19/how-an-aquaponics-system-work...

Thank you for posting this link.  I often find myself explaining in words how the system works.  This is the best demo I've seen!

Comment by David Schwinghamer on March 3, 2012 at 7:44am

There is also an improved system called Chop 2 which I am using, check it out.

Comment by John Malone on March 2, 2012 at 8:46pm

Something else that I'll be doing is having an overflow pipe in the growbeds to handle the situation that the bell siphon gets blocked somehow.  If you don't control the overflow correctly and direct it back to the sump the pump will keep pumping until the sump is empty and you'll have problems.  One, there will be water overflowing where it shouldn't and two, the sump will be empty so the pump can't pump water and you have the same effective situation as a failed pump.  

Here, again, a permanent air bubbler in your fish tank will save the fish.

You've got to look at your system and ask yourself all the horrible questions:

1) What if my pump dies?

2) What if I get a leak?

3) What if the plumbing clogs / blocks?

What if, what if, what if...

Then you figure the level of risk you are willing to take, and take it knowledgeably.

Comment by John Malone on March 2, 2012 at 8:37pm

Holly,  In a CHOP (Constant Height in fish tank, One Pump) system like the one in that link, the water flows to the grow bed via a gravity overflow.   i.e. as the water is pumped in to the fish tank, it overflows to the grow beds.  The big thing here is that it is NOT a siphon and it is not allowed to act as a siphon because then it has the possibility of emptying the fish tank completely, which would be bad.  Very bad.

If you look at the diagram closely you'll see an open pipe vent above the water line just under the words 'Fish Tank'.   This open pipe prevents any suction from happening and so there is no danger of a siphon event happening.  That means that if the pump fails the fish tank will drain to the level of the overflow pipe which is at the top of the fish tank.  Good.  Wet fish = Happy fish.

The worst case scenario in this design is if the pump dies at the exact time that the grow bed(s) are draining.  It's not all that likely, but you have to consider it.  Then the sump would fill up with the water contents of the grow bed(s).   So, to prevent the sump from overflowing you have to make sure that it can hold the water volume of all your grow beds combined.     This isn't as much as you'd think, considering that the grow beds are mostly filled with grow media.  

I found the volume density of various gravels on a website somewhere and you can safely assume that in a grow bed the media takes up 60% of the volume, so that means that when the grow bed is full the water takes up 40% of the volume, and probably less once you get plant roots and sludge and worms and etc.

Assuming that to be correct, the size of your sump needs to be 40% the volume of all your grow beds combined.  Then you'll never have a water disaster.

When considering breakdowns though, you also need to remember that the fish need oxygen which is provided by the circulation of the water.  If the pump stops the fish are going to suffocate and die rather quickly, in the order of hours.   One recommendation is having a backup (sump) pump on a car battery with a switch that triggers on if the power goes off and the main pump stops, so that the fish will survive.  This is how Murray Hallam does it in his video.

I'm considering a different plan which involves using a computer UPS (Uninterruptible Power Supply) to power the main pump if the power goes out.  But what happens if the power is OK and the pump dies for some other reason, say mechanical failure or blockage?  I'm sure that happens.  I'm trying to design some electronics (I'm a computer geek, so that's where I tend to default) to detect this and kick off the backup pump.

A much simpler solution, and one I'll probably end up doing myself, is to have a permanent air bubbler in the fish tank connected via the battery UPS.   They bubblers draw very little power and should run for a long time on the UPS and keep the fish alive even if something horrible happens to your pump.

Wow, that's a long post.  I hope it helps and doesn't have too many errors.

Comment by Dave & Yvonne Story on March 2, 2012 at 6:59pm

I like sharing.

As I often say, here you can learn, teach and have fun.

Comment by Dave & Yvonne Story on March 2, 2012 at 6:59pm

If you did not find your answer, let me know.

Comment by Holly Curtis on March 2, 2012 at 5:27pm

finding some of my own answers: pump animation: http://www.ecofilms.com.au/2010/06/19/how-an-aquaponics-system-work...

Comment by Holly Curtis on March 2, 2012 at 4:51pm

PS  Yes, my knowledge is very weak in some areas.  Thank you for your patience....

Comment by Holly Curtis on March 2, 2012 at 4:50pm

So...it sounds like a basic principal I missed is that if the fish tank is higher than the grow bed, use a siphon to get water out of the tank with the hose high enough in the tank that if the water level drops below the hose, thus stopping the siphon, the fish still have water.  Then use the pump to return water to the fish...if the pump fails the water drops and the siphon stops and the fish still have water...is that right?  This is an idea I haven't found yet .... this is most helpful.

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