Backyard Aquaponics
A place to discuss aquaponics

that would be my concern

Needs solids to collect in an area and switch a pump on now and then to purge them to the top of the beds...

But then most of the solids should be going through the pump and into the top bed, they will get trapped in this bed and break down, or if it's a floating raft you can have yabbies that will help consume the waste...

in a circular tank the solids collects in the middle

Hi,

While I think this design has merit, there are some issues to be resolved.

The solids issue doesn't concern me unduly......they will end up in the upper tier of grow beds particularly in a smaller system where the movement of the fish will ensure that they get into suspension (and within reach of the pump) pretty quickly.

With upper tier growbeds (if they were chosen over a header tank), the fact that the bottom tier grow beds are fed from the bottom (and drain the same way) is also no real issue because I believe that, so long as they remain in the system somewhere, it doesn't much matter where.

The main issues to be addressed (in my view) are the volume of the upper tier header tank or grow beds relative to the lower tier.......and how to maintain water levels (without daily topups).

On balance, it's worth resolving the problems for the prospective benefits that the system offers.

Gary

I don't think that daily topups will be required, at least not for most of the year, and certainly not here in Perth... Maybe some of you in FNQ may need to at some times of the year..

I've been wondering for a while about setting up a blue drum with a drip feed above my large system so that I know I can go away and 200L of water will be slowly added to the system. This would also be a convenient way to mature scheme water if the top was cut off the drum and covered with fly wire..

I would imagine that the best way to go, if both beds are going to be gravel beds, then the top one would be the same size as the bottom one.. And assuming that you had a 50% air gap in your gravel, then the fish tank would want to have half the surface area, of one of the growbeds.

Glad my whellie bin idea has sprouted some new idea's...

Thinking outside the box... One issue of using plastic containers etc haning of the outside, is are they UV stablised... Mute point i know...

I hope I'm being helpful. You guys definitely have the more hands on experience than me but I like to problem solve and think things through. Although it has been noted that sometimes I don't think them through enough.

Um.... I thought I'd dealt with a bunch of that stuff on page 2 of this thread. If it wasn't clear I can add pictures but since no one commented I thought I'd explained it at least adequately.

Top up will be really simple with a timed switch that turns the pump on every so often. While the solution I had that would work with a submersible pump will be prone to the tiny drain hole clogging in the header tank but I think it would work.

If the grow beds are filled with the same medium then top grow beds need to take a larger volume of water than the bottom grow beds and hence will need to be bigger. The ratio between the top and bottom grow beds is determined by the shape of the top of the FT and the void of the medium used in the grow beds.

Any solids that enter into the tidal growbed are more likely to be removed by the faster action of the outgoing tide (caused by pump) and hence as other have said will be collected in the F&D GB. Therefore the Tidal growbed is unlikely to have many if any solids from the FT collect in it. This could actually be another big advantage.

Since very few solids are deposited in the tidal GB you could use a finer medium like sand. This would provide a place to grow all those things that don't like growing in gravel (carrots and such).

Stuart

EB,



I think you misunderstood what I was getting at.

In order to drain the bottom tier, you are going to end up with the water that it contains plus a further amount from the fish tank.....all of which is going to have to be accommodated in the upper tier growbeds.

If we assume (for the purposes of the exercise) that the lower grow bed holds 100 litres of water and, to reduce the level to the point where it drains properly, we have to take another (say) 100 litres out of the fish tank, then the top grow bed will need to have a water capacity of 200 litres.

See what I mean? It's not an insurmountable problem but it needs to be taken account of in order to make the thing work.

Thinking about your suggestion of the 200 litre drum.....if you fill the drum and then put the bung back so that it's airtight.....and then have the outlet pipe at the exact depth that the water gets to when the lower tier is fully drained.....as the water evaporates, or is used by the plants, more water will flow from the drum in the exact amount that is required. It would work like a chook waterer. Similar to the drip feed idea but demand-driven.

Gary

Can anyone give me the void in various sandy like mediums they have used.

I toyed with this idea before... There are several advantages, as mentioned, the tidal growbed is virtually free, but remember that if you have a 1 m^2 tidal bed, and 1m^3 tank, you will need 3 of the 1 m^2 F/D beds to drain enough water from the tank and the tidal bed to get it to work.

For Top-ups, put a simple float valve (something like a toilet fill valve) where if the water drops below the level of the tidal bed, it adds water until its right at that level. Regardless of timing cycles, if the water got below that level, you're cutting into the water that the fish would need.

For solids and occaisonal flushing of the tidal bed, why not have part of the water return from the F/D go into the tidal GB? It would be pre-filtered from the F/D GBs, and would flush the Tidal beds without any additional trouble.

To expand on Joel's idea, you could set up a top tank with Yabbies, etc. have that dump into a barrelponics-type F/D, and then drain from that through the tidal GB into the main tank. One pump running continuously, a Raft/Yabbie tank, 3 F/D GBs, and a Tidal GB.

SC have a search, i think there may be some already listed somewhere. just set the search options to return posts not topics

Hi Stuart,

Take a container of a known volume (fitted with a drain) and fill it with the media that you are testing for void space. Add water until it is level with the top of the container. Drain the water and repeat the exercise (measuring the water as you go) and you will have the void space for the media that you are using.

The reason that I suggest that you fill the container and drain it before re-filling it and taking the measure is that, depending on which media you use, there may be some take up of water on the first fill.

Gary

Steeve
Did a search as you suggested and found lots of references to sand but didn't find any mentions of the void.

GD
Yeah thats how I know the void of the blue metal gravel that I've got here.
I've got some river sand coming tomorrow that I'll be doing a test batch of render with. Before I use it all up I'll measure the void and let peoples know.

STUART
its in there somewere i remember posting mine dont know where or how much

I have had a header tank working on my flood and drain for the last 6 months or so which auto keeps the water level for the system just right.
Murray