Ebb & Flow Rate and Regulation

[Steve Werlin]

I have a small indoor set-up with a 20 gallon aquarium.  My grow bed is fed by a pump from the fish tank.  It drains via a bell siphon into a reservoir.  And then the reservoir water is pumped back into the fish tank.

I've set both pumps to their lowest setting, but I think they still may be going too fast.  I read that the cycle should go through at least once per hour.  My system is cycling more like five times per hour.  Is this too frequent?  Is it possible for the ebb & flow rate to be too fast?

[RupertofOZ]

Steve, as a "general" rule... it's advise to turn over your system volume at least once per hour...

 

Turning over your volume more frequently is'nt a problem... unless the actual retention time is too short for complete nitrification... but that's a pretty rare event....

 

Are you sure that you are actually turning over the volume of your system water 5 times per hour.... or are you saying that your grow bed(s) only actually flood & drain... 5 times per hour??

 

There's a difference obviously... your grow bed volume might not be any where near your fish tank volume...

 

Even so... turning over the volume (water volume) of your grow bed(s).... should be close, or exceed your fish tank volume...

 

P.S.... I wish people would desist from using the term "ebb & flow".... rather than "flood & drain"...

 

Ebb & flow uses a timer based pump regime...and floods the grow bed from the bottom... up through the media....(excess overflows via a standpipe).... but then drains back... (after timer off).... through the pump line, and pump...

 

Flood & drain... whether continously pumped/siphon drained... or timer pumped/standpipe drained.... pumps to the top of the media... and fills top down... draining through a seperate drain line... not back through the pump...

 

IMO... "ebb & flow" has no place in solids/"dirty water" systems such as aquaponics...

[Steve Werlin]

Thanks, RupertofOZ.  

My fish tank is 20 gallons.  With the displacement caused by the media, the grow bed fills to about 15 gallons or so (maybe a little less) before the siphon starts.  As a way to control the output rate from the fish tank, and for aeration, I have a line redirecting water directly back into the fish tank from the outlet. So not all of the water being pumped actually cycles into the grow bed each time.

I meant to say that the siphon drains the grow bed about five times or so per hour.  So, no, not the entire volume of the fish tank.

From what you say, it sounds like it's not a problem for the siphon to flood and drain the grow bed as often as five times per hour, especially if the grow bed doesn't fill to the entire volume of the fish tank.  Is that correct?

I guess my only concern was about the plants.  Are the roots getting "too" inundated with water?  Do they need a longer exposure to oxygen before getting flooded again?

And yes, thank you for the lingo help -- I meant "flood and drain."

RupertofOZ said:

Steve, as a "general" rule... it's advise to turn over your system volume at least once per hour...

 

Turning over your volume more frequently is'nt a problem... unless the actual retention time is too short for complete nitrification... but that's a pretty rare event....

 

Are you sure that you are actually turning over the volume of your system water 5 times per hour.... or are you saying that your grow bed(s) only actually flood & drain... 5 times per hour??

 

There's a difference obviously... your grow bed volume might not be any where near your fish tank volume...

 

Even so... turning over the volume (water volume) of your grow bed(s).... should be close, or exceed your fish tank volume...

 

P.S.... I wish people would desist from using the term "ebb & flow".... rather than "flood & drain"...

 

Ebb & flow uses a timer based pump regime...and floods the grow bed from the bottom... up through the media....(excess overflows via a standpipe).... but then drains back... (after timer off).... through the pump line, and pump...

 

Flood & drain... whether continously pumped/siphon drained... or timer pumped/standpipe drained.... pumps to the top of the media... and fills top down... draining through a seperate drain line... not back through the pump...

 

IMO... "ebb & flow" has no place in solids/"dirty water" systems such as aquaponics...

[RupertofOZ]

 

From what you say, it sounds like it's not a problem for the siphon to flood and drain the grow bed as often as five times per hour, especially if the grow bed doesn't fill to the entire volume of the fish tank.  Is that correct?

 

Yes, and no.... it's not really a problem how fast the flood ^ drain is... or how many times it occurs.... but the "goal" is still to turn over the eqivalent of the system volume... (tank, sump, rafts).... once an hour...

 

I guess my only concern was about the plants.  Are the roots getting "too" inundated with water?  Do they need a longer exposure to oxygen before getting flooded again?

 

It would seem intuitive that might be the case.. but the water is continually oxygenated/re-oxygenated by the flood & drain action... and often, and advisably...., oxygen supplemented...

To the point where even constantly flooded systems, both raft and flood & drain... perform as well as other methodologies....

 

Here's a thread about some comparative flood & drain  trials BYAP conducted...

http://www.backyardaquaponics.com/forum/viewtopic.php?f=51&t=862