Backyard Aquaponics
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Growbed questions...
http://byap.backyardmagazines.com/forum/viewtopic.php?f=1&t=6838		 Page 1 of 1
Author:  DéjàVoodoo [ Jan 11th, '10, 10:28 ]
Post subject:  Growbed questions...
OK 30cm seems to be the standard GB depth and 60cm even seems to be used. Anyone try 90cm?

I am also curious about mixing media in the same growbed. I think I want to go 90cm (more filter - less yard used - kids still need a place to play), but clay balls would be too costly so I was thinking gravel on the bottom with the top 10 or 20cm clay balls. Then I got to thinking about cleaning the GB and was wondering if some sort of plastic mesh between the two media might be benificial. I plan on worms in the bed, so the mesh could not be to fine...any ideas?

I also have a pile of what we call Bull Rock in my yard...they are large pieces (mostly golfball to baseball size), can I get rid of them at the bottom of my growbed? Anyone know of PH problems with it? I guess I could throw some in a bucket of water and measure it if nobody knows.

Gonna start a thread of my own soon. Should break ground in the next couple weeks. Got my concrete guy over yesterday and got a quote for the poored concrete and digging work. The wife gave me the thumbs up! :cheers:

Not GB related, but I still need to find the burried power feed from the easement to the house. The power company is not required to mark it and I am pretty sure it runs through my sump site somewhere. Anyone know of a cheap way to locate it. I do know the starting point where it comes under the driveway and I know it is burried exactly 2 feet down. I tried the poke a rod in the ground method, but quickly got frustrated by rocks and roots in the way. Some sort of cheap EMF detector would be great! Once I find it, I can adjust my plans around it.

Thanks for any help!
Mark
Author:  earthbound [ Jan 11th, '10, 10:45 ]
Post subject:  Re: Growbed questions...
Deeper will give you more area for the bacteria to populate, but the limiting factor will be the removal of nutrient from the system, the plants. You fish numbers are limited by plant numbers rather than filtration volume, unless you start doing water changes on a regular basis.
Author:  RupertofOZ [ Jan 11th, '10, 10:50 ]
Post subject:  Re: Growbed questions...
While you gain more filtration with a deeper bed... you don't gain any surface area for planting...

You'll also require about 2-3 times the volume of water each flood & drain... over and above a standard 30cm bed... don't foget to factor this in when designing the rest of the system....

Not sure I see the benefit of going so deep.... and I'd be curious as to water/oxygen flow and any possible buildup of solids in a bed of that depth.... would certainly be interesting to see how thay might perform over a year...
Author:  DéjàVoodoo [ Jan 11th, '10, 11:23 ]
Post subject:  Re: Growbed questions...
earthbound wrote:
Deeper will give you more area for the bacteria to populate, but the limiting factor will be the removal of nutrient from the system, the plants. You fish numbers are limited by plant numbers rather than filtration volume, unless you start doing water changes on a regular basis.


I would have to argue that it is not limited by the number of plants, but the plants ability to take up nutrients. For example, tomatoes are know to be heavy feeders. Even things such as bamboo, bananas, and passion fruit could easily take on all the nutients of a heavily stocked system with little surface area.

I could be wrong as usual though...
Mark
Author:  DéjàVoodoo [ Jan 11th, '10, 11:28 ]
Post subject:  Re: Growbed questions...
RupertofOZ wrote:
and I'd be curious as to water/oxygen flow and any possible buildup of solids in a bed of that depth.... would certainly be interesting to see how thay might perform over a year...


In the name of science - the call has been made by Rupe! Other then gravel, it will cost very little extra - so my thought is why not???

Mark
Author:  Simo [ Jan 11th, '10, 14:43 ]
Post subject:  Re: Growbed questions...
Check out viewtopic.php?f=18&t=2218&st=0&sk=t&sd=a&start=1245

OBO has done exactly what you suggested 90cm GB deep, cheap gravel on the bottom expanded clay on top.

Using large rock would dramatically reduce the biofiltration when compared to smaller gravel as the large rocks have a lower volume to surface area ratio so less bacteria per square foot of GB, it is the tiny little holes in the expanded clay that makes it so good for AP, they have a massive surface area to volume ratio and therefore can support more bactreria and convert more ammonia and nitrite in the same volume of GB as normal normal gravel.

Deeper GB will achieve more biofiltration but may not be worth the cost of the large GB unless you had the deep GB cheap and readily available like the ICBs OBO uses.
Author:  TCLynx [ Jan 12th, '10, 00:07 ]
Post subject:  Re: Growbed questions...
I'm using several deep grow beds (not as deep as OBO's as he is using IBC's as grow beds) but I have several 100 gallon rubermaid stock tanks as grow beds now and they are just over 2 feet deep. Yes I think bananas are a good choice for keeping up with the nutrients but they can also quickly outgrow the space as I found out. I will be trying some of the Truly Tiny variety to see if they might answer this issue for me.

Anyway, 30 cm is commonly thought as a really good minimum depth for flood and drain grow beds. 45-60 cm grow beds I think are actually really good for maximizing bio-filtration while still having a fair amount of planting space. Aquaponics really is a balancing act though and there are many many things that will affect the balance. The lovely BYAP systems are great but since we don't have access to such grow beds here, I'm actually quite partial to the stock tanks now. This leaves me open to doing the deep beds and if I have excess nitrates, I'll plant more stuff to put in NFT tubes or DWC beds to use up the excess nitrates without having to add more gravel than I need. Or I go water some of the dirt plants on occasion with AP water.

If you haven't already, I suggest reading the Basic Info and Useful info sections of the forum pretty thoroughly and then you might choose a couple or more of the big long member system threads to read though. Outbackozzie's system thread might be a good choice as you are talking about deep beds. His systems have gone from small half pipes all they way up to IBC's with barrels as well.

Good Luck with it all.
Author:  DéjàVoodoo [ Jan 12th, '10, 00:40 ]
Post subject:  Re: Growbed questions...
I have read yours and OBOs threads (although his I skimmed through some). I think I read all of yours and I started at the beginning of his again last night - they are long reads, but very inspiring. I have really enjoyed Nocky's thread as it is somewhat in line with my long term plans. I think I have watched every youtube video about AP and have made my way through much of these forums....what a great resource this place is. With a fixed square footage I am trying to maximize potential FT volume. There was some mention of vertical grow walls in another thread - looking into that also but other then strawberry towers, there is little info on them. Since I am building with concrete, just want to be sure I get it right. There won't be much room to go back and change things other then add a GB here and there. I will start with light stocking and build up from there.

Anyway - still some unanswered questions - like a plastic mesh between different media etc...

Thanks
Mark
Author:  Johnh [ Jan 12th, '10, 15:07 ]
Post subject:  Re: Growbed questions...
I think a divider between the different media would be a real pain in the A***
all the roots would get tangled in it and would be impossible to pull large plants out, even leaving the roots below the divider may present a problem - worms cant get rid of them until they break down which may be a long while for some larger plants. I think the cons definitly outweigh the pros . if you are careful removing old plants there won't be much mixing , and does it really matter anyway,
John
Author:  TCLynx [ Jan 12th, '10, 23:36 ]
Post subject:  Re: Growbed questions...
Dividing media. I wouldn't bother. You mention wanting to do it because of needing to clean the grow beds, well if you have plenty of grow bed for your fish tank volume, then most of the old timers here who have emptied a grow bed have found that they really don't need cleaning. (Provided the media is of appropriate size, too small media can get clogged up and not let water flow through so well.) The trick is having twice as much grow bed as fish tank and having the water feed to all the grow beds to share out the solids appropriately so they are not building up. Also, if planning to grow things like bananas, bamboo, etc, I would definitely avoid putting any sort of divider down in the grow beds.

There is not a lot of info about strawberry towers since they are kinda an off shoot. Like NFT pipes and such, the water going to a strawberry tower usually needs to be filtered at least somewhat or they will clog and have issues. Since the water is trickling through a strawberry tower and the media is not necessarily getting evenly wet, you probably can't really count the media volume in a strawberry tower much as part of the bio-filter.

If you design a CHIFT PIST system with a clean water sump, then the pump flow could be split off to feed towers and NFT since the water in the sump is clean without having to deal with extra filtration for them. However, if going with a really big system, using CHIFT PIST makes it more difficult to use a spider valve though it can be done it definitely adds some complexity. A simple system can use a spider valve quite easily but then you would need some separate way of feeding towers and NFT pipes.
Author:  Sminfiddle [ Jan 12th, '10, 23:58 ]
Post subject:  Re: Growbed questions...
DéjàVoodoo wrote:

Not GB related, but I still need to find the buried power feed from the easement to the house. The power company is not required to mark it and I am pretty sure it runs through my sump site somewhere. Anyone know of a cheap way to locate it...
Thanks for any help!
Mark


Mark,
Have you tried calling 811? I see it on trucks here.
notvalidinOZ

Rick
Author:  DéjàVoodoo [ Jan 13th, '10, 02:03 ]
Post subject:  Re: Growbed questions...
ya - they came out and mark utilities, just not the feed to the house. Then on the website it says they are not required to do so, and gives numbers of private companies that will do it for a fee.

Mark
Author:  Simo [ Jan 13th, '10, 06:19 ]
Post subject:  Re: Growbed questions...
Try local government, mine stores building approval plans which sometimes have utilities marked.
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