Are the fish dead yet? - Santee, CA system

dstjohn99

So, I finished converting my 3rd media bed to sand. That completes the Tilapia system conversion to iavs methods. I was using pool filter sand. It worked very well on my first bed, but I'm not sold on the 2nd bed. The filter sand does not wick moisture very well, so it's hard to start new seeds.

The first bed I had access to the drain, like in an AP system. I was able to use a standpipe to raise the water level in the sand, and run something like a constant flood to speed the bacteria colonization and keep the sand damp. The damp sand was excellent for starting seeds, and after thigs got going I removed the standpipe and went pure iavs. By then the detritus layer had formed and I think between the roots and some algae in the sand, the water distributed very well and the plants have thrived!

I had some feedback on another group that drain access was not needed in iavs, etc. So for the 2nd bed I covered the drain. That meant I was never able to run a standpipe and raise the water level. It was difficult to get seeds sprouted, and even now many weeks later the bed is more like a desert. The water just pours through the sand and does not wick well to get the ridges moist. So the few plants I have established are doing well, but it's difficult to start anything else.

I poke down into the sand in bed #1, and it hold it's shape and is wet only 1/2" down. But bed #2 is all dry sand at the top, and it's an inch or so before there is moisture.

Attachment:

20210916_161035_resized_1 Bed 1.jpg [ 303.06 KiB | Viewed 3110 times ]

Attachment:

20210916_161018_resized_1 Bed 2.jpg [ 256.84 KiB | Viewed 3110 times ]

Bed #2:

Attachment:

20210923_084052_resized_1.jpg [ 321.26 KiB | Viewed 3110 times ]

I added some #20 silica sand along one edge (right side below), and it wicks moisture very well! It stays damp after the water flow stops and I was able to sprout some carrots, which don't like to be dry at all.

Attachment:

20210928_140926_resized.jpg [ 278.29 KiB | Viewed 3110 times ]

dstjohn99

So, for Bed #3, I did things differently. I still think #20 sand is a bit too fine, even though it passes the tests. So, I used #16 silica sand for this bed. I left access for the drain so I can use a standpipe again while it is needed.

Per recommendations from others, I did not use fabric to separate the sand from the drain. I just used some fine gravel. I also had some #12 sand which is kinda coarse, so I used it to surround the gravel, though this is not necessary. I had a few bags of filter sand left, so I used those in the bottom. Then I topped everything off with the #16 sand.

Here is how I set up the drain. I used a PVC ring to hold the gravel in place, then after it was surrounded by sand I removed it.

Attachment:

File comment: Drain configuration

20210928_133251_resized.jpg [ 227.79 KiB | Viewed 3108 times ]

Attachment:

File comment: Gravel in place

20210928_133546_resized.jpg [ 242.33 KiB | Viewed 3108 times ]

Attachment:

File comment: Filling around the gravel

20210928_133843_resized.jpg [ 322.93 KiB | Viewed 3108 times ]

Attachment:

File comment: Coarse sand covering gravel

20210928_133911_resized.jpg [ 288.01 KiB | Viewed 3108 times ]

Attachment:

File comment: Filter sand, coarse sand, gravel surrounding drain

20210928_134327_resized.jpg [ 246.1 KiB | Viewed 3108 times ]

Attachment:

File comment: Worm castings in troughs, standpipe in place, water flowing

20210928_181841_resized.jpg [ 316.81 KiB | Viewed 3108 times ]

skeggley

Awesome, taking notes, thanks for sharing.

dstjohn99

skeggley wrote:

Awesome, taking notes, thanks for sharing.

My pleasure. I love the low-maintenance no filters needed. The waste does seem to "digest" and not accumulate in thicker and thicker layers over time. But I'm definitely still trying to understand a few things. Like, if you need sand that flows freely, then the water never fills the bed. So how does the sand get wet where the plants need it?

I think over time as roots develop and waste breaks down that the water flow slows and spreads more. One person commented that my sand appears fine compared to what they use. I get that coarser sand will clog less (hey, how about some clay pebbles or media beds!?), but it presents a challenge for getting enough moisture near the surface for sprouting seeds. Will the sand "clog" over time? How much time?

I have six years of solid AP experience, but only a couple months with the sand gardening. I have one IBC system with 3 GBs now fully converted to sand. My other system has 9 media beds to convert and 3 DWC beds that will remain.

boss

This is such a cool design- I'll need to start from scratch now that everything burned to the ground. Oh well, our claim is in and the money will be available in January (next month) I'm jumping with excitement, finally

I think i'll do Brook trout again.
Brian

dstjohn99

boss wrote:

This is such a cool design- I'll need to start from scratch now that everything burned to the ground. Oh well, our claim is in and the money will be available in January (next month) I'm jumping with excitement, finally

I think i'll do Brook trout again.
Brian

I am excited to see you back Brian. I look forward to posts about your journey forward. You are one of the inspirations that drove me, and others, over the years when we used to have 20 posts a day on this forum. I do miss those times, but even I rarely visit here anymore.

Backyard Aquaponics
A place to discuss aquaponics