Backyard Aquaponics
A place to discuss aquaponics

Currently designing a large Flood and Drain system that will hopefully incorporate auto siphons in 12 bath tubs (thanks to EKB and other work!). Fish will be housed in a 3100L (2100 dia. X 860mm high) tank, one pump delivering water to grow beds, gravity return, one thing has been troubling me...

I plan a ratio of around 1(fish tank):1.2(grow beds). Taking into account that maybe 50% of grow beds is occupied by medium (correct if wrong ) I still need 1800L of water required to fill the grow beds, to flood all of them. This would mean the fish tank need to drop to around 350mm in order for this to happen. Obviously due to each bed location they will fill at slightly different rates but this seems like the fish won't end up with much water.

Any help with my pondering??

I know I have missed something, and hope my answer isn't else where in this forum (I have read posts for over 2 months now and this still isn't clear)

Try getting a 9L bucket of the medium you are going to use, then fill it with water measuring how much it takes to fill the air spaces, then you can work out how much it will take to fill your baths.

My large flood and drain takes about a third of the water in my fish tank to fill the growbeds, so the fish tank is constantly cycling between full and two thirds full.

Man, that was fast EB! Excellent idea re: bucket test

I've studied your book (excellent by-the-way) and noticed you have a sump tank, does this impact on the water level (i.e. not needing as much from the fish tank at any one time? I find it had to mentally visualise these things).

Also, I know both your pumps are operated via a float switch. Is it a coincidence that the floats arc range (between on and off) is enough water to flood your beds or is this adjustable. I have a pump arriving soon with option to fit a float switch, otherwise I will experiment with continuous running and hope the pump does not exceed the siphons ability to suck water from the grow beds.

I just realised you can only have a continuous running pump with siphons, other wise some beds will end up half full of water until the fish tank pump is switched on again?? (is this right)

Now I'm confused , I hope everyone else knows what I am talking (typing) about. ?

i think for a continuous flow pump, you should control inflow rate of the pump to the GB using ball valves. adjust the rate so that the input is slower than the siphon output. or maybe add a T-joint so some of the water from the pump output is redirected back into the tank so the inflow rate is slower than the siphon.

look at simmo7 system with control valves at his output from the pump
http://backyardaquaponics.com/forum/vie ... 07&start=0

Thanks for the further clarification easyihzy. Its slowly making sense!

Asi, it is definately an issue re dropping tank depth. Initially I had one tank only 600 mm deep, then realised to do anything like the size system I wanted, that i needed more tank volume, but more importantly, depth, so now I have 2 tanks joined together that go up and down in a tidal fashion. It's just one option to consider, means that the same volume can be pumped with only a 50% drop in the water depth.

hi i have 2000 litre fish tanks and900 litre grow bed and when i flood i use 300 litre my beds are filled with scoria hope this helps

that's pretty good, my 1000 litre beds each take 400 to fuill

My 600 ltr grow bed takes 187 litres of water to fill right to the top
Muzza

I know I keep harping on it, but mf has the best idea that I have seen and that is to set the fish tank at a constant level and have a sump tank that fluctuates with the GB intake; not only that, it grabs all the crap from the bottom of the tank and dumps it in the GBs and is not cycled via the pump

I agree - the challenge is then to find a sump which is big enough to hold a good capacity of water and that is not too deep as the grow-beds gravity feed back to the sump. I am happy to dig the sump into the ground - but I don't want to dig in too far (an effort as well as practicality thing, there are a lot of big rocks underground at my place).

I would like my sump to be at least 1000 litres (to easilly handle 4 of Murray's grow-beds).

and thus the interest in solenoid valves (and ball valves) so as to only hold volume for approx one GB at a time in reserve, unfortunately this then adds to the budget

Mate - I want ot go simple. I'm happy to pay the extra for the bigger sump and do away with solenoids, ball valves etc. Give me the LKB autosiphon any day.

Aw shucks - if we could only figure out a simpler way of feeding the GBs in series

There is the gravity feed from one to another - probably no good due to the necessary height of the first being a bugger (and also the height of the first bed needs to be lower than the height of the standpipe in the fish tank). Then there is the option of getting everything so perfectly the same that you can start the syphons at differnt times and they will stay syncronised (implausable I expect). The thing is that the beds are bound to run at different times meaning that it will be rare for all of them to be fully flooded at once. All the same it is for that point, which will ocurr every ?? hrs or minutes, that we need to cater for. Also would want some extra capacity to cater for inevitable loss of water from the system (evaporation and transpiration). I don't want to have to do top ups daily to prevent the sump from running dry.