Backyard Aquaponics
A place to discuss aquaponics

Nah, he just redefined it



The terminology is pretty tough because you can combine things in a number of ways. Consistently flowing hasn't been used until now - It's probably what we call Continuous Flow. Consistent F & D would then be Flood and Drain with Siphons/Continuous Flow which we usually just call Flood and Drain with Siphons.

Constant Flood - Bed is always flooded to a set depth using a standpipe (typically about 1 inch below the surface). I think most people probably are pumping 24/7 with Constant Flood. So really we typically mean Constant Flood/Continuous Flow based on Stuarts explanation.

Continuous Flow - Basically just water always flowing through the grow bed.

Timed Flood and Drain - Timer controls pump that floods bed and when the timer turns off the pump, the bed drains.



Flood and Drain with Siphons - Drains when the siphon kicks in. This is what you have Ben.

Hope that gives you the basic idea but don't really want to get into a long discussion on semantics. I can think of a lot of scenarios, like where the system is on a timer but uses autosiphons, what kind of system is it. I'd still call it F & D with Siphons but it does have a timer

Cheers

Flood and Drain with Siphons - Drains when the siphon kicks in
Thats what i have got, but i was thinking it might be two quick a cycle. the logest cycle i can acheave is about 23 minuites, depending on the header tank height,
I have just found a low (no) pressure valve with a timer, going to try it on one of the beds on a 1 hour flood and syphon drain and see if there is any plant growth difference

@Scotty - Hi Scotty, can you please point me in the right direction for a better understanding on how Timed Flood and Drain system function? Sorry for being a tad lazy

So much information to sieve through.

Thanks

Regards

I'm not even sure where to begin looking, maybe just a search on the forum. It's really very simple though.

You have an electrical outlet with a timer that is set to whatever interval you want and a pump is hooked to this. So basically the pump goes on and off when the timer supplies electricity. When the pump is going it supplies water to the grow bed (either directly or indirectly). In each grow bed is a standpipe that sets the maximum water level. Once the water level in the grow bed reaches the top of the standpipe it overflows back to the sump and will keep doing this until the pump stops. Usually there is a second, much smaller hole near the base of the standpipe that continues draining the bed after the pump stops so that less water sits stagnant till the next cycle. If I remember right many people use the cycle of 15 minutes on and 45 minutes off during each hour but plants can adjust to other cycles and some plants just need less water. With orchids for example, once a day or less may be adequate.

So if you want to do timed flood and drain, you still want to move the volume of your Fish Tank once per hour. This means that your pump will need to pump that volume in 15 minutes (at whatever head height you're pumping to) assuming you're using the cycle at 15 minutes on and 45 minutes off.

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Johnh - As long as your turning over the Fish Tank volume at least once per hour the cycle time isn't that critical. I've had autosiphons cycle at 6 minute intervals with the plants doing well. The plants will adjust over time. Try the valves if you like and let us know how they work - I might find a use for these in another part of the system

I am having a bit of a problem visualizing this valve without something overflowing if the pump is always going

I'm outraged. How dare you.




Remember no one has done the research (or at least not published it) so we don't actually know but...

To a degree that is going to depend on the plant.

Something like a tomato is probably not going to care at all. Tomatoes send their roots every where and will be able to follow the water down so that the plant can always have wet roots. In addition the gravel will stay wet for quite a while allowing the roots to continue to draw nutrients even while not submerged.

Water melon on the other hand that are very shallow rooted may be effected.

As to the water being cleaner. The rate at which the plants draw nutrients is pretty slow you would have to leave the water there a long time to see an appreciable difference in nutrient concentrations. Second the nutrient concentrations and basically independent of how clean the water is. If the nutrient levels are so high that they are lowering water quality and adversely affecting the fish then they are too high for both the fish and the plants. As long as they are not too high nutrient concentrations are not a measure of water quality. Rather it is the solids and oxygen concentration that are the measurement of water "cleanness".

Ideal flooding and draining regime is more likely to be dependant on evaporation rates within the media and oxygen delivery to the media ecosystem rather than nutrient uptake.

The rate at which the plants draw nutrients is pretty slow you would have to leave the water there a long time to see an appreciable difference in nutrient concentrations.

I think you can use Hydro flood and drain timings as an example of this.

Ideal flooding and draining regime is more likely to be dependant on evaporation rates within the media and oxygen delivery to the media ecosystem rather than nutrient uptake.

In my opinion this is the right answer.

(I am having a bit of a problem visualizing this valve without something overflowing if the pump is always going )
I am still pumping to the header tank (fish tank) at the moment on a float switch. it just wont drain the header tank as fast as it will only drain to the grow bed once every hour. I put some tomato cuttings in the grow bed to see it there is enough water to keep them alive and they have picked up well so the gravel is keeping wet enough.
I can see a bonus with the timer valve as i can decrease the flood cycle in the colder monthes when not to much is growing. therefor saving the pump on time.

I cant quite visualise what you are describing (a sketch would really help) but I think I can visualise a header tank dumping to the GBs on a regular basis?

Regardless the speed at which water flows, fills and drains is the combination of flow and pipe sizes. It is quite common for people to under size their pipes. I know I did enough times and it was making that mistake once too many times that spurred me to thoroughly learn and understand hydrodynamics.


That is going to depend on what else your system is doing. Your plants might have slowed down but if you are raising a cold water fish they might be wanting more food in which case you would probably feed them a bit more to save your fingers at feeding time. In that case you might want to increase the pumping rate so that the increased waste load is better dealt with.

In practice I don't see a backyard system getting much if any benefit from making such adjustments. The first reason being that its very hard for them to know what adjustments to make, BYAP systems don't tend to be capable of adjustment easily, BYAPers generally have no way of monitoring the effects of their adjustments (like decreased [O2] due to decreased flow for example) and getting an extra 2 to 5% of production isn't really important to a backyard operation where as low maintenance and stability are.

johna - it would be interesting to see how your system is setup, have you started a system thread?

Cheers