Backyard Aquaponics
A place to discuss aquaponics

Even better than a UPS is a car battery, inverter, and battery charger. 1 Landcruiser size battery will give you 20 hours of running time @ 30w.

For your above diagram, 25mm poly will be fine from the pump to the fish tank, at least 32mm (highly reccomend 40mm) pvc from the fish tank to the growbeds, and at least 19mm poly from each growbed back to the sump.

Smaller just does not work over time, the biofilm blocks it. Been there done that.

After derekh kindly showed me his system yesterday, I'm now in 2 minds as to which way to go.

One practical difference for me is the levels of the FT/GB would need to differ for each system:

System A would mean lowering the FT (it's currently sitting on 2 pallets), and would mean cutting the barrels lengthwise to keep them lower - any higher and the wife and I would struggle to reach them! Some people mentioned they prefer not to cut them this way, but given they'll only be for a herb garden, bed depth isn't an issue. I do admit, it means more work in setting up a stand/frame for them to sit on though.

System B allows me to keep the GBs lower, thus giving me a choice of cutting them lengthwise or widthwise, but also means drilling an overflow from the FT. Small an issue it may be, but for some reason I'd prefer not to have to do this.

I'm not sure of the benefits a ST has. His sytem doesn't use one, and appears to work just fine. Anyone care to provide pros/cons?

I'm keen to get going on either system tomorrow. Before making the plunge, I'd really appreciate some advice to the 2 options mentioned in the previous post.

Anybody?

sorry ryan, been a bit busy lol

System B is the way to go mate, a lot safer for the fish, the pump will last longer, you cant pump the fish tank dry if something goes wrong with the plumbing.

Drilling a hole is nothing bad.

but its not the end of the world if you go the other way, it will still work well - whatever you feel happiest with

I would go with system B also. If you really can't figure out a good way to drill and plumb thought the fish tank, you can still use a no holes overflow method.

As to your pump running constantly or the sump running dry. It all depends on the size of the sump tank. If the sump tank is big enough to hold all the water from the grow beds plus some, you should be able to run the pump all the time and let auto siphons drain the grow beds to give you flood and drain. I usually pretend that the grow beds will hold half their volume in water after they are filled with gravel, it is an easy way to make sure you don't undersize your sump because you need a little depth for the pump to operate plus some leeway for evaporation and topping up etc, and I like to be able to slip a low level top up float valve in below the normal low water mark but above pump danger level so that I don't need to worry about it running dry from evaporation when I go away for a weekend.
So if you have a big enough sump, you can let your pump run all the time. If your sump is not big enough, it makes doing CHIFT PIST with only the one pump kinda difficult since the sump won't hold enough water to flood all your grow beds in one go. In which case you would need to either cascade some of your grow beds or use multiple pumps on timers to flood different beds at different times.

What size is your sump tank?

I think system B is a probably more sophisticated and probably more resilient.

My sump is a bathtub, but it's difficult to know exactly it's capacity. I assume it's about 200 litres, but will try and work out a more exact volume today. I fear it may not be big enough, or deep enough for the pump, for system B, which I was planning to use 2 x 200L barrels.

In summary, system B would have:
400-450L in the FT
2 x 200L x ~40% for the GBs (160L)
~200L in the ST

Would this be suitable, and if so, is it correct to assume that on startup I fill both the FT and ST (giving a total water volume of about 550-600L)?

Given the ST would not be refilled until the GBs drain, it appears that there is a risk of running it dry. Do STs usually contain a continuous pump, or can it be set on a timer to only pump when the ST is full?

Since you wish to get your system up and running and these are the parts you have, here is what I would suggest doing.

Still set it up as B
Place your sump tank in a location where it will be resonably easy to replace or add another tank to later. (ya know, bath tubs make pretty good grow beds too in case you haven't cut your barrels up yet, perhpas you want to leave a barrel mostly intact and sink it a little way into the ground as your sump with only a big enough hole in the top for plumbing and accessing the pump.)

Anyway, hook your drains up on the grow beds to be slow drains or do loop siphons that you can adjust to a very low water level. If you do slow drains, leave your options open so you could swap over to siphons later. This adjustability and setting the flood level low, will allow you to keep from draining your sump dry. If you go with loop siphons, then let the pump run continuous. If you go with a slow drain set up, you will have to use a timer which hopefully can be set to less time than it takes for your pump to drain the sump tank dry.

The problem with using a float switch in this single pump set up, if you have auto siphons, your grow beds may fill most of the way up and the switch turns the pump off and everything just sits there since the beds didn't fill up enough to kick on the auto siphons and so they never drain to the sump tank and the pump just sits there in several inches of water. Or if you are going with slow drain (which would be the way to go if you have a sump pump with float switch set up) then it will sort of work but the beds may never fill as full as you might want them. This might not be terrible but you loose a bit of the biofilter capacity since less of your gravel is getting wet regularly.

You really do want a little bigger sump than half your growbed capacity. Have you concidered using the two barrels hooked together as your sump and then use the bathtub as your first grow bed. Then you can add more grow beds as you get the stuff to do it with.

Awh I've done it now, thrown a wrench into the design huh?

On another angle, I guess system B work fine if I lessen the GBs to either 200 or 300 litres... correct?

Right it would. You just can't support as many fish with the lesser amount of grow bed.

So, with 450L FT, 300L GB and 200L ST, how many fish would I be looking at?

Assuming 3kg (fish) : 100ltr (filtration) .....

9kg of fish.... harvest at plate size... @500gm....

20 fish max....

I'm not the expert on proper stocking density but let me see what I can remember. (you should probably do some searching around on the forum to find more numbers. Look for threads about stocking density and grow bed ratios and such.)

Rupert, I thought it was 2-3 kg of fish per 100 l of water providing that you have the 2:1 grow bed:fish tank ratio?

for 200 l of grow bed, probably 2-3 kg of fish

Put it this way. The standard rule of thumb (which are all aprox of course) is 2:1 Grow bed:fish tank and at that ratio perhaps 2-3 kg of fish per 100 l of fish tank. People then start talking about feed rates to grow beds and heck, I don't know how many grams of food my fish get. Anyway, back to the ratio. If the two to one ratio says I should have 200 l of gravel to that 100 l of fish tank for 2-3 kg of fish so I take that to mean that I could have 2-3 kg of fish in any amount of fish tank larger than 100 l so long as I have 200 l of grow bed to support it. For 300 l of grow bed, figure perhaps 3-4.5 kg of fish. The tricky part, perhaps that system might support 100s of tiny fish but only a few really large fish. So I guess you better get going on the big system huh and this could be your fingerling tank?


If you can add sump capacity later, you can add more grow beds.

Do remember that a new system takes time to get cycled properly and you don't want hungry fish like bara as you are trying to cycle.....well then again, the bara eating each other will take care of the culling so you don't have as many big fish as you started with small ones......

Anyway, what kind of fish are you thinking about?

I highly recommend fishless cycling.

Bugger it - it seems whilst the sump idea might be better, I think I might go with System A after all.

Being my first setup, I want to keep things as simple as possible, and I like the simplicity of system A.

Excuse me if I've offended anyone for seemingly ignoring their advice - quite the contrary... it's all been very valuable and I think my future system will employ the sump method.

The only real question I have with system A is, how do I stop the pump from sucking up the fish?

BTW, intending to go with silver perch at this stage.

Most pumps have some type of screen and therefore sucking up the fish is not a problem. Even when I've had major leaks, I've never run my pump fully dry or had my fish without water. Why, because the pump inlet is at least 50mm off the bottom and the fish can survive for short periods with low water levels. Also, most of my major leaks occurred back in the auto-syphon days.

Good luck and have fun with the build, whatever option you choose.

cheers
Derek

keeping pumps from sucking up fish is important! My first loss was from pump sucking.

Depends on the type of pump. If it is a submersible pump, I would probably place it in a milk crate and wrap the whole thing up in a net or mesh bag of an appropriate size to keep the fish out. You will need to pull this all out on occasion to clean it.

If you are installing an in line pump of some sort, put a basket or intake grill of appropriate size on the intake end of the pipe.

Some people make their own intake grills by cutting slits in a large bit of PVC pipe with a cap on one end, other end hooks up to the pump intake. You can also probably buy one of these with or without an extra bag to go around the grill, the often call them a lake or canal screen here.

Is the tank round? If so, put the pump or the intake in the middle and have the drains from the grow beds enter the tank at a bit of an angle so as to create a swirling current that should help the solids go to the center of the tank to be picked up by the pump.

no offense taken, we know this is only your first system and you will be doing others and you have to work with what you have to hand.

To help make harvest easier, perhaps you sneak the grow beds up onto the deck? If it can support the weight. Or you just put them high enough that your access them from on the deck?

Good luck