Backyard Aquaponics
A place to discuss aquaponics

I am putting together my first system, and I'd like to use a bell siphon. From what I've read and seen, in a traditional ebb and flow system should run 15 minutes on and 45 minutes off. This probably ensures that the roots don't stay too wet, and I would think if you are using worms, that they don't drown? Now with a bell siphon system, it sounds like the pump is always running, so the grow bed is always either filling with water or completely full (just before the siphon trips). A lot of people seem to say that the bell siphon setup may actually be better for the bacteria in the system and the plants, but it seems like there is no real off time to allow the roots to not get too wet. I realize that it takes a while to fill a grow bed, so the roots get some dry time, but I can't imagine it is the same dry time as 45 minutes of in a traditional timed ebb and flow.

Can anyone comment on this?

Hi and welcome to the forum

In AP because the water is well oxygenated, the plants dont need "dry" time so to speak. Many systems out there run constantly flooded. The reason this works is because the plants have a supply of oxygen and nutrient rich water to survive.

Think of it this way - if you put a plant in a bucket of water it will die in time as there is minimal O2 available and will eventually deplete and the plant will die... but if you put an aerator in that bucket with a nutrient solution it will grow and thrive.

Hope this helps.

Thank you for the reply. In your experience, does a bell siphon system work better than a timed ebb and flow?

There is a thread on here somewhere where BYAP trialled 3 systems. I will see if I can find it and post a link.

Update: link is:
viewtopic.php?f=51&t=8621&hilit=byap+trial

That is like asking someone what is the best religion! I happen to be a member of the Affnanian Church of the Advanced Siphon. While we have the option to convert to constant flood, most of it's adherents prefer to siphon. The Order of the Timed seem happy, but the rigid on/off times regulated by a piece of electronics is adding more hardware than the Affnanians prefer. There are some other sects, like the First Church of the Loop, and the fussy Universal Church of the Breather Tube. As an Affnanian, I am not opposed to those in the Congregation of the Constant Flood, though sometimes it's members are less tolerant of Affnanians.

We accept all religions here...

Does that include those from the Church of Pissed-up-testi-costicles?...

The thing to remember with AP is that in simplicity a AP system has a fish tank, grow bed and pump. These systems can be changed any time to be either flood and drain with timer, flood and drain with syphon or constant flooded.

Try one and if you dont like your progress try something different.

There is no right or wrong.

Yep, Kevin and Shirl are more than welcome, just no one from The Festival of life though please....

I would've thought, being from Kal n'all, that Charlie would've been a member fersure... seeing as that's where Pastor Kev hails from!... but obviously not!

Ok, few more questions. I plan to have a 4.5'x2' grow bed for my 55 gal tanks. When this is filled with expanded shale, does anyone know an easy way to calculate how much water it will take to flood to 10" high in the bed,? I'm trying to figure how low the tank is going to be at the top of the flood cycle before the siphon trips, i.e. if big tilapia will have to swim sideways for a bit til the bed drains.

When working with siphons, one really should have a sump.

A rough rule of thumb with most gravel types... is that GB's with 300mm (12") deep gravel flooded to 250mm (10") take about 1/3 the total gravel volume, in water, to flood the bed to 10"...

ie: a GB with 300mm (12") deep gravel, totalling say 300L (80 gal)... would take rougly 100L (27 gal) of water to flood it to 250mm (10")

I did an experiment regarding this a couple of months back. With Hydroton expanded clay the water volume required to get to the top of a 250mm standpipe worked out to be 34%... you couldn't get much closer to 1/3. Others that have used 20mm (3/4") blue metal gravel have quoted similar %'s of water required.

and...

I found the amount of water in a grow bed of scoria changed dramatically over time.

When it was new I would guess it took twice as much water as it did after a year or so. (based on the changing depth of sump in my flood and drain system)

Things I've put it down to include root mass, fish solids still being processed, but trapped in the media, bio slime holding back more water, settling of media, and there's probably a half a litre of worms living there as well

Ok, so my 4.5'x2'x1' grow bed will hold roughly 67 gallons, so a third of that is about 22 gallons, which will drop the water level in my 55 gallon tank about 40%, or about 8", leaving about 13" of water. Someone here mentioned a sump-- would this be some type of auxiliary reservoir that would help keep the fish tank full when the grow bed is flooded to peak just before the siphon triggers? Or is there some other way to compensate for the water level drop in the tank, or do the fish just deal with it?

Once I saw Affnan's videos, I pretty much considered myself an Affnanian .