Aquaponic Gardening

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I am a newbie and was just curious about the timing between a full grow bed and fully drained bed? Is it ba to have them too quick or too slow? Right now I have a 25 gallon GB that fills in near 10 mins and drains in near 4 mins.

Let me know what you know.

Thanks.

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Just about everybody who ever said anything on the topic on this and some other forums. I can't think of a single person who has made a statement saying otherwise. That's not to say that that necessarily makes it true, but I tend to take advice that comes from certain long standing aquapons to heart. So this is something that I payed attention to and designed in for.

It may somewhat be dependent on stocking densities, but I've only heard even higher turn overs (twice per hour etc...) ever mentioned...never lower... If you, (or anyone) have any thoughts otherwise I would very much like to hear them. What/why?

The pumping at least the volume of your fish tank once per hour recommendation is a "rule of thumb" or a good starting point for system design, just like the 12 inch deep beds or how much grow bed one should have in relationship to the fish tank volume.  They are all rules of thumb to help new people put together a system that will be easy/functional without too much extra effort.

Yes there are plenty of people out there getting away with different things.  It is because so many of the "things" depend on other things.  Like how hot/dry it is and what plants are in the beds and how strong the nutrients are (Lots of hydro plants will actually start to wilt if you water them too often with strong nutrient solutions.)  Anyway.  If you are running with siphons, your cycles will be as long as they are since to greatly affect the speed at which a siphon bed cycles you have to change a lot.  So if the siphon is working well, don't fix it.

If you are doing timed flood and drain you might want to adjust the cycling based on season and heat since during hot weather you may need to flood more often and during the hot season you need more filtration going to keep up with the fish too.

Turning over the water once or more per hour is mainly about water quality and aeration.  If you don't have many fish and lots of water you might not "have" to pump that much but as you reduce the amount of pumping you do, please monitor your water quality to figure out when you have gone too far.

Dr Wilson Lennard and Dr James Rakocy have recommended that your fish tank volume be turned over 1x per hour.

Community AP said:

Who said AP water needs to be turned over once per hour? 

Yes Vlad, Nelson & Pade run a side system that is constant flood media beds which they use to deal with the solids they have pulled out of the UVI type system. They have air stones running the length of them every 2 or 4 feet. Dr. Lennard has stated that plants need far less DO than fish so you could probably get away with less than you would in a fish tank.

Vlad Jovanovic said:

I'm gonna go out on a limb here...but i'm thinking that the whole 15 minute thing has much more to do with the fact that most timers are built with 15 minute increments on their dials than any scientific research. This 15 minute number (like how grow beds need be 12" not more not less) was probably picked up on and folks ran with it, and it is now carved in AP stone. Be it timers or siphons. So don't mess with it

I could be wrong though.

@Jonathan, don't people run constant flood, constant flow systems without those problems you mentioned? I guess adequate oxygenation would be key...

Jonathan,

     Plants may not NEED as much DO as the fish do (as in the plants probably won't die overnight from lack of DO as the fish may), but you may well find that plants will do far better with more DO than is even safe for the fish.  Some plants will be fine with minimal DO while others will languish if there isn't enough.

I agree TC, I have seen DWC rafts with the air stone down the middle of the raft where the plants in the middle are bigger than the plants on either edge. It is an anecdotal observation, but I am planing to test this with my system to confirm it..

TCLynx said:

Jonathan,

     Plants may not NEED as much DO as the fish do (as in the plants probably won't die overnight from lack of DO as the fish may), but you may well find that plants will do far better with more DO than is even safe for the fish.  Some plants will be fine with minimal DO while others will languish if there isn't enough.

This blanket statement comes from RAS world and is implemented in high density system where carrying capacity has exceeded the biological filtration ability and drum filters are employed for solids management and liquid oxygen is employed to sustain aquatic life for longer than 10 minutes during a power failure.  It specifically applies to raceway system that are open loop.  Technically all systems are open loop because we are putting in and taking away but in the previous statement it refers to freshwater sources being passed through the raceways which require at minimum 1 turnover per hour which is carried over to the closed loop RAS "as a rule".

A balanced small scale non commercial aquaponics setup designed according to proper carry capacity doesn't fall into this category.

Jonathan Kadish said:

Dr Wilson Lennard and Dr James Rakocy have recommended that your fish tank volume be turned over 1x per hour.

Community AP said:

Who said AP water needs to be turned over once per hour? 

roots being massive (really thick and wide) is not neccesarily a good thing, its the tiny white fluffy feeder root hairs that provide a higher surface area and better nutrient uptake, plant roots completely submerged (or overwatered) will often have roots like this, yes they work but how well? i fail to get my roots as fluffy and healthy looking in AP as i do in hydro or or aeroponics but then again you have a massive amount of bacteria surrounding your roots and this helps massively with nutrient uptake.

personally my system fills slower then dumps all the water pretty quick, with the bed being right above the tank the quick dump of water seems to agitate the tank better and help oxygenate the water reckon mine fills in about ten to 15 and dump in less than 5, but i have never timed them to be honest.

It really depends on the type of hydroponics. Aero is the ultimate in root development.  You are correct in surface area of roots.  Roots absorb nutrients, they don't suck them up like a milkshake.  But it is hard to understand that given there are so many variables in play between systems with so many different results and the plants do much better when compared to soil media, sometimes.


Missed your reply TC before commenting. I can agree that one turnover per hour should be a guideline for beginners to help maintain stability.  I get far better results by not turning over water that frequently. But my goals are more about reducing fish stress and keeping the kids happy  I focus more on plant growth and media methods with matched carrying loads.  I have seen on these forums that people get too excited and do grossly overstock without regard to filtration. Stressed fish affect the whole system as much as stressed plants.


TCLynx said:

The pumping at least the volume of your fish tank once per hour recommendation is a "rule of thumb" or a good starting point for system design, just like the 12 inch deep beds or how much grow bed one should have in relationship to the fish tank volume.  They are all rules of thumb to help new people put together a system that will be easy/functional without too much extra effort.

Yes there are plenty of people out there getting away with different things.  It is because so many of the "things" depend on other things.  Like how hot/dry it is and what plants are in the beds and how strong the nutrients are (Lots of hydro plants will actually start to wilt if you water them too often with strong nutrient solutions.)  Anyway.  If you are running with siphons, your cycles will be as long as they are since to greatly affect the speed at which a siphon bed cycles you have to change a lot.  So if the siphon is working well, don't fix it.

If you are doing timed flood and drain you might want to adjust the cycling based on season and heat since during hot weather you may need to flood more often and during the hot season you need more filtration going to keep up with the fish too.

Turning over the water once or more per hour is mainly about water quality and aeration.  If you don't have many fish and lots of water you might not "have" to pump that much but as you reduce the amount of pumping you do, please monitor your water quality to figure out when you have gone too far.

I have a constant fllos and drain system the fills in about 2 min and drains in about 30 secs. I have lettuce, broccoli, strawberries, and onions growing in my system without any fear of root rote or anything. I think that the ratio of time of flood and drain doesn't matter as much unless it's a plant that doesn't like to be in constant water (IE, bell peppers)

Community AP said:

Atmospheric pressure drives the drain.  I have to laugh when I hear people say the the water sucks down air into the growbed when it drains.  That's nonsense. The weight of the atmosphere pushes down to the degree you let it.

What we are trying to do with FD is maximum root exposure to air without drying theroot system or the BB colony.  Some hydro growers flood and drain six times a day. Are they right or wrong?  It doesnt really matter. I flood and drain twice per hour without timers. Why? Because of the evaporation and drying caused by Texas heat on lava rocks. My personal opinion of someone that says 15 minutes as a rule tells me that they really dont know.  Use your judgement.  The less you water the better the root system will be for absorbing moisture.  Check out some aeroponics on youtube to see how well developed a root system can actually become when it's not constantly saturated.

If it is working for you then that is great.  My point was less flooding equals better development. I have two fast flows for herbs and testing but my slow fill on 35 minutes produces better results, even with peppers.

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