Backyard Aquaponics
A place to discuss aquaponics

When the different gravels vary in shape it is quite difficult to tell what the displacement will be without doing a bucket test.

My gravel that I have used in my little test setup is 10mm drainage gravel (you know the grey stuff). It is less round than the gravel that EB and many others use - it is sort of flat. Accordingly displacement would (I imagine - I haven't tested it yet) be greater (ie there would be less air in between).

This is why I am interested in optimum displacement. I could test my gravel to make sure there is enough space for root development. I expect there is as the plants I have in the test bed have well developed root systems, in fact the corriander roots grew right through the bottom of the bed and down the drain pipe.

Checked on temps again tonight at 8pm.

Outside temp is 10C

All heaters were initially set to around 18C

Temp measured at between 17.6C (surface) and 18.2C (at depth) with two of the three heaters out on temperature. (off)

have raised one of the heaters to 20C as i should get this easy. Actually bugger it, i'll go and set one at 22C, one at 23C and one at 24C. I'm hoping that i'll be able to maintain 24C with only one heater once its up at temp.
looking good This would cost me less than 1 dollar per day, and only during the coldest months of the year. COOL (I mean warm)

The only trouble i see is that heat loss increases with temperature gradient IE: the greater the difference between tank and outside temp the more heat loss. However most of the "outside" consists of dirt around the tank, so that will eventually come up in temp too!

I'm Stoked.

Will post more results tomorrow night.

Hmmm, time for some more crazy ideas........ i might partition the surface of the water at about 2/3 mark and float duckweed / azolla in the larger section, this should act as a blanket. (probably more of a problem with a larger green house, Hmmmmmmmmmmm.

the clay balls are going for less then a dollar a litre at some of the hydroponics shops. i got mine for $35 per fifty litre bag, and the best quote i got was $28 for 50 litres. thats in brisbane

Nick is correct $35 per 50LT bag at this place

http://users.bigpond.net.au/nutriflo/index.html

Seems like i'm not the only night owl

Those prices are nice..... I knew I was paying too much when the hydro shop lady said she could give them to me for half price as a special deal....

I will tell. you will get lush green algae on top from phosphates. No phosphates = no ATP = no veggies so you can't win. You can grow with the algae but it competes heavily for oxygen and provides a perfect set-up for an algal bloom in your fish should conditions be met. Land based plants (ie your veggies) will uptake phosphorus more readily than algae but if the algae on top is getting the nutrients first they will proliferate.

I speak from experience.

Now lets find out how to add water under the beds surface, this I want to know too.

In my little test bed I have the pierced poly pipe a few centimeters under the surface. I then get no splash - just a bit of mist now and again. The surface of gravel is wet though. A disadvantage with the buried pipe is it is taht it can't simply be lifted to clear out debri, roots etc. I was thinking that if I do the same thing with my big bed, I might have some gravel contained in netting which sits over the pipes. I could then lift this up to access pipes. Mind u I guess the roots would end up growing into the netted gravel . What is really needed here is some sort of easy to remove mulch on top of the bed, covering the pipes. Organic is not good, so how about some much larger pebles than the growing medium or even some slate tile cutoffs just coverring the pipes so as not to interfere with the plants. Holes should be drilled in pipes so that water is directed downwards of course.

How about one central pipe that stays under the gravel and smaller easily removable side 'arms' for ease of use cleaning.

At what depth does water input need to be in clay balls to stop the top being wet? Anyone?

The pipes do not need to be under the surface, so long as the holes are drilled into the under side of the irrigation piping, and this sits on the surface of the gravel you should have no problems. I have no algae problems at all on the growbeds.... Touch wood.

With my large system I don't see any water at all when the pump is on, it shoots straight down into the gravel with no splash or spray. I have found with another small system that the pump was a bit to strong and it was pumping water out of the holes under pressure, this was causing it to spray and splash a bit so I turned the pump down a little and it's worked a treat....

Nice one earthbound. Thank you.

Catch 22 guys, i wanted even water coverage over the clay, which certainly have, not as much of a problem in a flood and drain system, but in cont. flow if the holes are only in the bottom or the pipe is buried then only a fraction of the clay will be wetted, which means that only a fraction of the media is osting bacteria.

I'm not so sure about that Steve. Once the gravel (or in your case clay) becomes wet the water may keep spreading out a bit through capillary action (probably not sticktly through this because of stones being so dense and not realy absorbing the water - but have used this term to help explain what I am getting at). I have found that in my bed - which has the pipe slightly burried, the water does spread. The deeper you go, the wider the spread is. The roots will seek out the water - so should be okay. I need be, could always give the gravel a water now and again for the first couple of weeks until the roots get deeper into the gravel.

Having said this, I agree flood and drain is for favorable re wetting of medium (less pipe required also) but this is not always possible.

I get what you're saying VB, but i'm more worried about the bacteria efficiency than the plant roots, thats why trickle filters in high end aquariums (the blue balls that are built into a back panel of glass) are SOOOOOOO effective.
They are meant to be a far superior filter due to the fact than in other types filters water generally find the path of least resistance. Thats my thory behind making the spray bar like that.
The bacteria are like a production line they need constant supply of raw products.
That 60L tub sould be able to provide enough beacterial activity to keep my ammonia and nitrites at zero, even with 40 fast growing perch. The nitrates (plant food) will probably accumulate though, becasue the amount of plants will be quite low.

I'll definatly need to revise the design once i get copious amounts of algae
Still this is the beauty of having a place like this to share ideas

Okay. In that case I think multiple bars would be the go to keep the clay wet.

probably. just like in EB's book. Doh. i often try and reinvent the whell