Backyard Aquaponics
A place to discuss aquaponics

Yes i think a water readings would be good because for some reason there may be more nitrates in one than the other

In terms of water quality this week, The timed system(3) still showed low levels of Ammonia and Nitrite, 0.25ppm for both, but they seem to finally be on the way down without us holding back the feed too much. The other two systems had a 0 reading for both. The nitrate levels are all the same, at around 5ppm.

The fish in system 3 have not shown any signs of being affected by the NH/NO2 readings at this stage and are always hungry...its hard to not feed them more!

I read with interest the experiment being done to determine the best aquaponics technique.
A similar experiment was carried out by Lennard and Leonard and the results also showed a clear advantage to constant flow technique. Another experiment was conducted by Storey and showed a distinct advantage to the NFT, a similar technique as the nutrients are constantly flowing although at a very low rate; millimetres in the bottom of a gulley as opposed to 30 cm or so in a tank.
I might seet up two systems to begin with, both in 1000 litre tanks. One might be a constant flood to a depth of a few cm below the gravel and one, that I am excited about, will be 90 mm pipe, also filled with coarse pebbles or scoria, running a minimal flow using a smaller pump.
Great website and chat forum everyone. It is very interesting and nice to see everyone is very friendly.

Storey. N.. An aquaponic system: Component comparisons and applications. M.S. dissertation, University of Wyoming, United States -- Wyoming.

WILSON A. LENNARD∗ and BRIAN V. LEONARD. A comparison of reciprocating flow versus constant flow in an integrated, gravel bed, aquaponic test system. Aquaculture International 12: 539–553, 2004.

Are we talking about a constant flow fully flooded bed? Or is it drained?

A reason for less water useage in System 3 ( constant flood ) could be that the constant flood may keep the GB media cooler and therefor less evaporation. Especially in the full sun.
What are the water temp variances between the systems.
Just MHM.(muses)
I just turned my timer to full flood from about 4am to 7pm. Then 15min on 45 off overnight. Was doing 15 45 , 24-7 before.
My full flood is via Standard BYAP standpipe in 300mm bluemetal.

Hmm, I dunno if Lennards system was continuously flooded, or just continuous flow... As with all things AP.... "it depends on soooo much..."


See much of Lennards trials were only done over twelve months as well, and hey, as we know things change so much over time.... Thats why these trials we are doing here are not to be considered a be all and end all, just interesting information over 12 months of operation.. Perhaps, all things willing these may run longer, would be great to run them for a couple of years so that solids build up, root build up etc can come into play...

Skipd.... the 3rd system is 15/45 flood and drain... Sorry.....

I tell you, I really expected it to be more in the third because of the plant growth, bet we will see what happens... Was just looking this evening and I thing the CF (system 2) is passing system 3 for silver beat growth...

Another cool thing with Constant flood, for my system would be that I could fit a fair bit more water in FT.
As you say EB long term trail would be great

Bugger, better go and change that timer and there goes that theory.

OK, I'm confused. I thought the 3rd bed was F&D. Isn't that a totally different issue than CHIFT PIST? My outdoor system is CHIFT PIST and F&D. What am I missing here?

I am not super familiar with all of the terminology here but I believe the CHIFT would incorporate a sump(which is where the water levels would very) where in some other flood and drain systems the FT is acting as the sump. CHIFT can still be flood and drain, or it can go into DWC tanks, vertical towers, etc.

As for the low evap in the CF tank, it's got to be due to the surface area. When it is constantly flooded, you have just the surface area of the trough coming in contact with the water. When it floods and then drains, a bunch of moisture is left in the media, which then comes into contact with air and can evaporate easier. Instead of having a 2d surface for evaporation, you have a 3d surface if that makes sense. Seems the evaporation out of the media bed out weighs the evaporation from having the constant splashing back into the FT.

Not following your logic Ryan...

The constantly flooded system (#2).... is the system that has suffered the greatest water loss....

System 3 is on a timer with a pumping cycle of 15 on, 45 off.... And yeah I guess what VB was talking about is probably closer to system number 1, most cift pist system I know are probably running siphons, I dunno, this is where AP becomes so tricky, so many people running so many variations.


So far, early indications are that system 3 with 15/45 timed cycle is showing less water consumption than the others, CF system 2 is actually showing greatest water consumption so far... BUT, these are only very preliminary, and very rough... Further results required to get a better idea...

Intuitively... I would have expected system #2 to have suffered the greatest evaporation... as more surface of the water is exposed to the heat of the day... for longer... in fact virtually constantly...

And as the timed F&D system has a drain/dry stage... I'd have expected it to have the lowest rate... and so it seems...

Yeah, I got mixed up with which system was which. Still, it seems you would have more surface area for evap in a flood and drain application. I havent done evaporation experiments before so the results are interesting to read. Going forward it will have a lot to do with plant size(and transpiration rates) as well.