Backyard Aquaponics
A place to discuss aquaponics

OK - I think that covers most of the electronics - now some info on the structural framework.

Frame
During one of our design meetings we came up with the concept of having the tank in the center surrounded by grow beds. Well we had a few issues to work out including access to the tank for feeding, observation etc of the fish and the method of supporting the grow beds. We had seen that other people have used a variety of methods to support the grow beds above their fish tank including the use of concrete blocks. A timber frame was suggested immediately and as I had recently built a kitchen table and bed out of timber it got the go ahead.

Here is a picture of the frame without the grow bed bucket support platforms. Basically an A-Frame design with three sides fitted for grow beds and the backside to provide access to the fish tank which will sit in the centre.



Tank and Gravel Fill
The tank has been buried approximately half under ground so that the grow beds are at the right height for us to access. However I was worried that the weight of the frame+filled grow beds would be to much for the small bearing area of each of the four frame legs. This could lead to the frame settling relative to the tank and could even end up with the frame resting on top of the tank. To support the four legs we made up some small concrete pads and filled the area beneath each pad with gravel to a depth of 0.5m. Hopefully this should provide enough support.



Concrete pads are placed upside down on gravel "footings" at each corner and frame legs then on top of pads.



Finally here is a picture with the tank, gravel, footings and frame in place. Two of the grow bed support platforms have been nailed in place.



So how's the design working out? Obviously the system is not fully operational yet but we have the following concerns:

* laterally the frame is very stiff longitudinally it is less so and we have added a brace (plank of timber near the top of frame) to stiffen in this direction. This has helped markedly though we may need to stiffen more as it is further loaded. So far with three beds loaded it is OK.
* at the back where we access the tank the ground is starting to press into the tank - we will need to provide some timber/concrete here to stabilise the ground in this area.

Otherwise grow beds seem to be at the right height and the design is coming together as expected.

Hi APP,
Just a couple of structural suggestions.
Diagonal bracing will strengthen your A frame as well as preventing anti-torsion failure.
Collar ties will prevent A frame leg spread and provide further bracing. The piece of ply, IMHO, will not be enough when the frame is fully loaded to prevent some sort of failure if the structure is knocked or otherwise disturbed.
You will have to unzip the PDF I have sketched for you, as this forum does not support posting PDF files.

Cheers IanK

Ian

Thank you very much for your sketch. My original thoughts were some what inline with yours as I had wanted to put a wire cross bracing on the front side above and below the grow bed platform. I wanted the back left open to provide better "non shin damaging" access.

I know there are wire bracing systems that have threaded "winders" to tension the bracing in each direction. I went hunting around here for this type of setup but with my limited spanish I couldn't find what I was after. Hence the plank.

So from your sketch your suggesting wire, steel rod, metal straps or timber. Timber I can definitely get and most probably wire as well.

With the timber would you suggest putting one diagonal member on the front side of the leg and the other on the backside OR cutting a grove mid length and attaching both diagonals on say the front side.

With the wire I don't know how I would tension it once it is in place - presumably it would require tensioning.

Any thoughts on these ideas?

I'm less worried about the legs spreading - though a mate of mine has suggested that I should put a cross member at the bottom of the "A" for this purpose and also to provide a greater bearing surface on the ground. I'll give it some more thought...

APP,
Just took some photos from around the house you may be able to use to explain what you need to use for what you finally come up with.




If you use timber, then yes, put to the back and front of "A" frame leg. Don't cut the legs, it will only weaken them. You can use thin strips of ply if you wish as they work in tension, so thick pieces of timber aren't really required.

Cheers IanK

Thanks Ian - that should be a big help. The first picture you posted (img0818) was what I originally had in mind - though I'll also give the timber option some more though.

Appreciate the photos (they'll be worth any number of my spanish words).

Actually Ian just went out to take a fresh look at the setup and the tank will impede any bracing on the bottom third of the frame.

On the front side I think I could put a single large cross brace on the top two thirds of the frame and on the back side a smaller one in the middle third of the frame without impeding leg room or tank access.

Well was doing some laundry in town today next to a hardware store I don't normally go to and they had turnbuckles hanging on the wall. So I decided to take Ian's advice and put in some bracing - so in I went and out I came with some wire and two turnbuckles.

Due to the way the frame sits around the tank there is limited locations to put in cross bracing. I originally wanted to stay away from the back of the frame (where the tank is accessed) but this ended up being the best place structurally for some diagonal bracing.





I thought the wire might be a bit to thin but it seems to have tensioned up nicely and has significantly stiffened the frame up. I'll more then likely put a slightly smaller diagonal on the front side of the frame located above the grow bed platforms. I plan on leaving the plank in place as it is providing structural compressive strength to counteract the tensile forces of the bracing.

Access to the tank has been impeded slightly but should not cause to many problems.

OK here are some pics of the grow beds and loop auto syphon system.

We had quite a limited choice when it came to grow beds and these buckets ended up being the best option - they hold about 80l and cost about US$5 ea. We hope to end up with six of these - so around 500l of media.


We decided to use loop syphons to drain the grow beds.You can see the connection at the bottom of the bucket in the picture above. PVC pipe and connections (3/4") and plastic tube (1/2") which are all common here and an o-ring as a rubber seal.


Drain cover is shown below to prevent gravel from entering the syphons.




The loop syphons seem reliable at the moment though I know some people have had problems with them. We tested three sizes of plastic tube (1", 3/4" and 1/2") and the 1/2" seemed the easiest to trigger and also allows a longer drain time. O-ring sela seems to be doing the job - no leaks but then there isn't much pressure...

Hi,
Just another observation, the clear tube used for your Loop Siphons will eventually clog up with algae if you don't paint them or stop direct sunlight getting to them.
It's all looking good at the moment, I hope you continue just as sucessfully in the coming activities (Especially when you get Fish!!)

Cheers IanK

Ok did some water/gravel tests as TCLinx suggested. The tests have been carried out using a 6 in 1 strip test kit - we'll be getting a liquid test kit later next week. Two tests were carried out; both containing a sample of water only and a sample of water + gravel. In test 1 the gravel had been in the water for 12hrs in test 2 for two days.



So the first test seemed to suggest that the gravel has a big impact on water pH, the second suggests the water also has a high pH. We are going to do a third test using local "purified water" again with samples of water only and water + gravel. We will also redo some/all of the tests when we get the liquid test kit.

Any thoughts from these test results?

Pictures of test strips here if useful: https://sites.google.com/site/aquapanaponics/4-project-updates

Thanks for the advice - attacked them with some duct tape. Thought that might be better then the questionable paint they have around here.

Cheers

Matt

To some extent the pH difference could also be due to the fact that water right out of a pipe usually has dissolved carbon dioxide in it which will cause a low pH reading but once the CO2 has outgassed, the pH is more accurate. (my tap water pH will read 7 if I check the pH right away but if I bubble it overnight it will read over 8.)

The gravel you tested, was it well washed before the test?

Next test, remember the kids volcano experiment with baking soda and vinegar, that is sort of what we will check here. To see if the rocks have carbonate in them by using vinegar. It might be worth putting a hand full of your washed gravel into a cup of vinegar and see if it fizzes up terribly or not. If it fizzes up then there is probably a lot of carbonate in the rock which will be bad for your system pH long term (fish won't mind and the bacteria would be fine at a pH of 8 but few plants grow well with a pH that high.)

If your gravel is not a problem, don't worry to much about the source water being hard and starting with a high pH since that will come down over time since the bacterial action tends to acidify the water as your system cycles up. It might be worth adding a little acid to the water in the system to get it down to say 7.6 before you start fishless cycling or cycling with fish but that might not be needed as my first two systems cycled up fine even starting at a pH of 8.

I have some experience with media that keeps the pH high, luckily for me the shells I used buffer to 7.6 which while a bit high for many plants to thrive to their fullest, this pH still works for aquaponics. So if by adding some acid to your water, you can get the pH down to 7.6 and then add your gravel and the probably dose again with acid till you get the pH down to 7.6 (each time dosing might take a few days) then hopefully it will all stabilize and the pH won't pop back up over 8. If this is the case, then your gravel should still work. If the pH with the gravel tends to keep popping back up between 8 and 8.4 you may really struggle to grow much other than algae and water cress long term.

TCLynx - thanks for the great reply.

Don't know if it makes any difference to your thoughts above but the water we have been testing with so far is water from our well - not sure if outgassing will apply to it?

I carried out the vinegar test with a "representative" sample of nine different types of rock from one of my grow beds. Here are the results, of the 9 sample rocks:

2 - inert no reaction
2 - almost inert very little reaction
2 - occasional fine bubbles coming of the surface of rock
3 - definite reaction with a very fine constant stream of bubbles coming out of one or two small holes in rock

I also tested some small bits of egg shell. These were immediately covered with bubbles on the surface of the shell a much more vigorous reaction compared to any of the rock samples.

To me this suggests that the rocks around here have some lime stone(?) in them, though they are predominately of other material or most of the lime stone has already been eaten away.

Unless you have some suggestions I think we will do the following:

1) wait until we get our half decent liquid test kit on friday
2) carry out pH tests of the following samples:
->a) bottled purified water (not sure how good this will be as a control)
->b) our well water
->c) bottled water + gravel (soaked for 2 days)
->d) well water + gravel (soaked for 2 days)
3) if above tests suggest that the gravel doesn't look good, we'll see how easy it is to collect "inert type rocks" and if it is feasible to obtain these in quantity then repeat tests with a couple of handfuls of these rocks...

If anyone has any great/different thoughts/ideas please let us know.

OK - got the liquid test kit and did some pH tests today. Water straight from the well pH ~7.4 and water from the system (that has been circulating through the gravel) pH ~ 8.2.

I guess my first question is - is the high pH likely to be due only to the gravel or could there be other factors/variables that are lifting the pH that I am not considering???

I'm thinking the next step is to dose the system with some sort of acid (lemon juice) to bring down the pH and then to test the pH over the next 2 or 3 days. At the same time I'll repeat some of the tests above to see if I can confirm that the gravel is what is causing the high pH. Any thoughts on how much lemon juice to add to 650L of water?

Cheers!

OK we have been carrying out some experiments adding lemon juice to the system and measuring the pH. The system is set to fill the grow beds twice each hour during the day light hours. Here are the results:

02 Dec pH 8.2
+ juice of 8 lemons
03 Dec pH 7.5
+ juice of 4 lemons
04 Dec pH 7.5
+ juice 4 lemons
06 Dec pH 7.5
+ juice 15 lemons (pH after adding 6.6)
07 Dec pH 6.8
08 Dec pH 7.5

Does this indicate that there is limestone in our gravel which is buffering the pH of the system up? Is the system the way it is a lost cause? Any thoughts appreciated....