Backyard Aquaponics
A place to discuss aquaponics

Hi,
after reading this very informative thread, im considering changing my system.
one bed i have has a looped siphon (draining 4 half blue barrels plumbed together) and it is 1 metre above fish tank, when this dumps there a lot of agitation of fish tank.
I was of the belief that this would be beneficial in terms of adding DO to FT.
disadvantages of my set up are; the fluctuation in FT water level, energy consumption ,noise, also the water level in grow beds is only at the peak for a short time; this trial suggests that plants/ bacteria dont mind being more flooded.

It is interesting that F&D doesn't adversely impact on DO, due to the fact that pump is running 1/4 of the time.
Fish in F&D trial system are doing well, this indicates that DO is not compromised
A timed system such as this, uses a fraction of the energy consumption.

so basically i want to change to a timed system but i want to make sure fish don't suffer


Do you have additional air pumps used in the trail, if so what is the capacity?

thanks for reading
cheers
ben
(I am using , GB=400lt, 10lt/min air pump ,4500 lt water pump , in 800 lt FT with 30 x 150mm silver perch)

Well Carl did some further recordings for the system yesterday as it's now been over 12 months we have been keeping the records. He weighed a sample of fish from each system, 6 from each and we have some interesting results.

the spread of weights in each system was similar

System 1
194
166
180
220
202
384
Total 1346g

System 2
214
280
124
238
320
228
Total 1404g

System 3
228
244
178
360
156
350
Total 1516g

So then he averaged the weights out of the fish for the total number in each tank so he could work out feed conversion ratios seeing that we know the feed rates. Though now I look at his workings I think there needs to be an allowance for the starting weight of the fish when they went in, so these figures are slightly skewed, but only a little. I'll try and juggle them later to include their starting weights.

System 1
5288g / 5607g = 0.94%

System 2
5746g / 5616g = 1.02%

System 3
6195g / 6315g = 0.98%

It seems like the Silver perch have been eating algae in the system as thats a better than 1:1 ratio.

I believe they are running air to each tank.

Now just because the pump is not constantly running doesn't mean the beds are not constantly draining so in timed flood and drain there is generally at least a trickle of water splashing back into the fish tank. Now this might not be enough water movement to keep a heavily stocked fish tank aerated, especially during hot weather but in flood and drain at least the water is unlikely to be stripped of dissolved oxygen after spending time in the grow bed. (Constant flood the bacteria and roots have no choice but to get their dissolved oxygen from the water since they don't have access to the air.)

Now doing constant pumping with siphons for flood and drain is likely using a smaller pump, if you switch to timed flood and drain you need a pump big enough to move the entire volume of your fish tank in the 15 minutes (or whatever) at the height needed so the energy savings might not be as big as you are thinking unless you are currently running a pump that is 4 times bigger than needed and will simply be able to put it on a timer.

Switching to timed flood and drain will not make the water level fluctuations in the fish tank any less. If you want less fluctuation you might put your beds on separate siphons or set a couple of them to constant flood and leave some on siphons with the constant pumping. If you switch to timed, then the water fluctuation will stay just as extreme unless you get a sequencing valve but then you won't be saving on electricity and will probably need a repeat cycle timer as well as a pump strong enough to work a sequencing valve.

Hi TCLynx,
thanks for the information,
have a good one,
cheers
ben

Interesting thread EB. I gather its still going to continue for a while as no total water use or total vegie produce. Look forward to seeing final results

______________
i was young and stupid once, i'm not that young now

@benwalters this might be a solution to an ultra low power system suitable for solar, based on the results of these BYAP system trials

Absolutely outstanding thread, as a newbie I've learnt a lot from it.

I'm looking at expanding my F/D system but have been grappling with how to increase my sump volume. The answer is constant flood, which I wouldn't have considered but for this thread.

Thanks for all the time and effort you've put into this experiment.



Did you mean 94%, 102%, and 98% ?

What's the expected FCR for Silver Perch?
Google suggests somewhere around 1.3 to 2.0, but you seem to be getting 1 to 1 (even allowing for the skew of start weights)
Are they very efficient algae eaters?

I'm far from an expert, but I'd say there's some flying insects, and kids feeding them bits of hotdog bun involved.

I know that's what I'd do if I was a kid with a hotdog in a shop with some fish, and I think all kids carry food at all times these days

We had some kid visit us and found the goat, all three sheep, the emu, and the pig chasing them all over the place because they had their school lunch from two days ago in their pocket or something equally as interesting.

And if the customer knows silvers, there would be a bit of plucking some produce from the grow beds as well I think. I cant go past my fish without giving them something, and more often than not it's just a lettuce leaf or similar.

Perhaps the odd insect, but definitely not kids feeding things to the fish. Whenever we have people in the shop staff are out there, and those three systems would be least likely to be fed because you can't see the fish with the nets over the tanks.

Here are come pics from this morning..

Sys1


Sys2


Sys3


Sys1


Sys2


Sys3


Sys1


Sys2


Sys3


We won't be doing weekly tests any more. We have over 12 months of data so now we will just monitor. We might still keep measuring the feed because thats easy, three different tubs, one for each system, but the weekly water tests and top up water measurements and photos from different angles won't be happening.

Hi Earthbound
i was wondering what size air pumps are running in trial fish tanks???,

(I would have thought autosiphon system would have a DO advantage over other systems
this is why i initially used autosiphon , Im currently converting to a more timed / flooded system after reading this post, but i hope im still getting enough air for my SP...)

happy new year to all APers
ben

People often get a bit hung up on DO levels, perhaps it's because most people can't measure it. The systems as they are, don't need air pumps. When they are stocked to their recommended levels (20-25 fish) the return water flow is enough to keep the water oxygenated. The air pumps we use are only small and only there for backup when the power goes out they have an inbuilt battery.

So many variables with this experiment but the flood and drain seems to be the go IMO.

As EB says, a modestly stocked system that is properly fed (no uneaten feed or fish waste accumulating in the tank) can usually get by with just the water flow and backup. However I found in one of my systems that come really warm weather, (water staying over 27 C night and getting over 30 C during the day) My fish kinda quit eating until I added a large amount of air bubbling into the tank. Very warm water doesn't hold as much dissolved oxygen so it gets used up faster.

So if there was no kids involved that's a pretty amazing result for silvers. That alone was worth finding out, because everything I've read says you need much more feed than that. Yet another advantage of not over stocking no doubt. (plenty of algae to go round)

Another amazing outcome of this test has been to show how resilient the general idea of aquaponics is.

Regardless of what you do, as long as you feed to within your system and cycle for a bit before adding too much load, aquaponics just works and isn't some insanely complicated thing that some of the junk on the net would have you believe.

I was very lucky to land at BYAP rather than getting sucked into one of the scam sites.

This has been a very informative test, and thanks again for spending all the money to build, install, maintain, and record it all.

It's great to see someone do the test just in case it was worth doing something different, and putting in the thousands of dollars just to find out.


Muchas gracias.