Backyard Aquaponics
A place to discuss aquaponics

Its interesting to see how different aged GB's perform in the same system. I started out with river rock and gravel then later added clay filled GB's. I will stick with at least top dressed in clay from now on. I've been stuck for time of late so I have GB's that I really need to put plants in and others that really need some taken out of. I transplanted a few cauliflowers from a younger GB because of overplanting. I didn't really know how moving plants would go so I picked the weaker ones first. Today I gave away another cauliflowers(I do this a lot cos there are so many ) that was the largest so far and it only dawned on me later that it was a runt that I had transplanted and I really should start taking photos again. The move to an older GB allowed the plant to over take its mates. More room would of played a part as well as F&D differences. It just interesting to see how an AP system gets better with age. Also that the 20 odd plants I pulled out for the chooks could of been saved but there really is still too many of these cauliflowers. I had also moved some to a newer GB but the growth has been slow.

Yep, growbeds just get better with age...

Have you made any comparisons, one way or the other, between gravel filled beds and clay filled??

F&F made some comparisons and I believe they are still running. Last time I heard he believed there was very little if any difference in growth rate of his crops. That's not to say there are no differences, just that he did not notice any (and neither did I for that matter when I visited earlier this year).

We trialled different media at the shop starting around May last year and found little to no difference in the first 6 months or so. The media included blue metal, diatomite, gravel and expanded clay.
The heavier media compacted and has become prone to flooding making it far more difficult to establish new successions of planting. Diatomite is simply too wet and prone to fungal disease. This trial was due more to the types of media than age of the system, but seems to prove my statement of "If the first expense is the last expense, it is the least expense".

I expect the shapes of the gravel has a bit more to do with the compacting than the weight does. I've found that the river rock doesn't really compact though it is quite heavy, the river rocks are generally more rounded though. The shells tend to compact more and there are far more flat surfaces on the shells. I would expect the blue metal (or granite) to compact the most with it's weight and flat surfaces while clay balls will probably compact the least because they are round and light. Scoria/lava rock will be somewhere in between on the compaction scale.

I have a 1000ltr gravel GB top dressed with a 100mm of clay. The gravel is old but the clay was added at the same time as the new gb's. It performs like an aged GB so its more what is under the surface that seems to count. The clay makes it easier to work with and plant into. Surface heat of the media is also better with the clay.