Backyard Aquaponics
A place to discuss aquaponics

How much does sand cost compared to gravel? The reason I ask is that you could have one ginormous biofilter. Set it up like people do with natural pools. Then you wouldn't even need to setup separate grow beds.

Its pool season here, so lots of people are getting swimming pools installed and they need to get rid of the dirt which is mainly clean sand here. thus we are known as "Sandgropers".

I can get fairly clean sand delivered to my door for free, getting it to my pool is more problematic, but doable with a little digger or mini loader.

Gravel would cost about $20 to $30 per m² so for my pool it would be around $1000. then I would need to wash it and cart it out back to the pool.

but would all that gravel lead to anaerobic conditions?

A little anaerobic is actually a good thing. That is the way nature is. If you look at natural pools, they have considerable amounts of gravel. I would probably build a large media guard in the deep end to act as the sump, then pump up from there to the fish tank. An airlift pump would likely do the trick. It would be lower energy, especially if you kept the water level in the gravel as high as you would have it in the fish tank, and would result in highly oxygenated water entering your fish tank.

interesting idea Ronmaggi, but I'm not sure of the mechanics is it:-

Fill pool with gravel leaving dished pond for FT, a bit worried about stability of the FT or would I use a plastic FT ( holes in base) in the gravel?

A deep well media guard with an air lift so water gets drawn through gravel and back to FT. maybe the GB could be one giant wicking bed?

I used my daughters paint sparkle program to hash out a diagram. It is much simpler than you mentioned. The fish tank could be made from the media guard of your choice, or what ever. You could use something solid, but I think that if you used a plastic mesh, perhaps wraped around PVC put together into the shape you want the fish tank, that would make water flow through easier. Anyway, the air lift, in purple, would simply push water from the bottom of the sump back up to the fish tank. It, in turn, would flow out of the fish tank as more water rushes in, and is drawn through the gravel back to the sump well, where it is pushed back up again. I would be hesitant about using wicking beds. However all of the gravel area would be one giant media bed. The drawbacks would be with that ammount of water, it would take a heck of a lot of fish to power it, and that the grow bed would be at ground level, which would mean stooping down to harvest, sow, and maintain.

thanks Ronmaggi, that's sort of what I thought. 30m³ is One heck of a lot of gravel, my incentive for the sand fill is because its cheap here, gravel is another plentiful item in these parts however 30m³ of gravel will cost about $4200 delivered.

It's all to hard, might be easier to forget it and just fill the and pave pool over.

Not too hard. Build your media guards, have the gravel company dump it into the pool. Fill with water, run the pool filter until the water is clear. Add fish and plants. As for the money part... I usually tell my customers at work to just rob a bank...

Ha Ha Ha Your banks must be different to ours!

Our banks rob us.

It goes both ways here. That is why I use a credit union instead of a bank.

All banks suck! Use a local bank but even they can be shitty

how about the stability of the gravel FT part. most people here seem adamant in having spotlessly clean fish tanks! all that loose gravel would be at risk of collecting a layer of crud which would be hard to clean-out.
Would there be issues having a huge mass of gravel and water?

I would have all that gravel behind a plastic hardware net. As for perfectly clean, I would imagine that it would fall between the gravel to be mineralized. Especially if your airlift pump has a bit of volume. The better question in my opinion is weather an impeller pump or an airlift would be more efficient at this point. I personally like the idea of an airlift for the additional oxygenation it provides. But someone with more airlift experience might be better able to inform us.

Too bad about all the problems your having mate. Hate to say it but maybe it'll be easier to fill it and set up a IBC system or a flash one from BYAP.
BTW i thought we were called sandgropers because these little critters

I caught two trout on the weekend using mole crickets as bait. Even trout of 400-500g only seem to take small crickets, based on my recent experience.

thanks Matyh, but I don't let the facts get in the way of a good story, in any case they live in sandy soil which is what we have in abundance.

Funny how when we hear them chirping at night it's "oh how cute, we have frogs in the garden" then when to kids see the mole cricket / sandgroper it's "eew yuck get it away"

PLJ did you catch the trout in your big concrete tank?

As an update for my system, there is actually some growth happening albeit slow, the pac choy and broccoli are being decimated by diamond back moths. decided to sacrifice them and the birds and wasps are getting a good feed from the grubs.

Also saw a nice sized frog hopping around the other night.

the fish are feeding as often as I chuck food in.

but I have lost a couple of yabbies, maybe they a fighting each other?
saw one fairly large one cruising around with no claws!