Backyard Aquaponics
A place to discuss aquaponics

Last year was my first for Aquaponics growing...I mostly grew lettuce in a flood and drain system with coconut coir in 3" baskets. They grew well so I thought I would expand to other plants this year....but am running into some germination problems.

For all my experiments, I prepared a set of pots with coir and another set with potting soil (since I still plant a regular garden). Everything is kept indoors at about 72 degrees. The coir isn't in the FD system yet...I just have them sitting in trays with my soil pots. All my seeds in the potting soil germinated. Here's my germination rate with the coir:

radish: 100%
green been: 100% no surprise here, you can practically spit on a bean and it will grow.
lettuce: 100%
spinach: 25%
tomato: 0% (nada)

The coir stays really wet. I just watered it once a week and I think it's still too wet. I'm assuming that the seeds are just rotting....?

I haven't tried it yet, but I may plant some seeds in 3/8" gravel....or maybe a mixture of both? It's expensive to buy river gravel, but I can get a pickup truck load of crushed granite for 12 bucks for a quarry near my house. It's very sharp...I"m hoping it doesn't damage anything. For your viewing pleasure, I've included photos of my coir and gravel!

Any suggestions would be appreciated. Thanks!

-Rob T.

No one has any suggestions??? Where's the love? (sniff)

From my experience coir remains too wet in flood and drain setups, I use it in a root vegetable setup but this uses a constant low flow wicking type effect. I have tried using small amounts to improve root humidity at the surface for small recently emerged seedlings.

The problem with sharp gravel is on the hands if you are working in it, or if you have easily damaged growbeds i.e. pond liner they might cut and leak.

Ditto.... flood & drain... too wet...

Drip irrigated, OK.... but needs to be a really slow drip... as above...

Or hand watered... once a week...

ROZ with watering once a week do you think nutrients are ok?
I remember your mentioning that in AP the nutrients are constantly being added so dilution is of little issue, but with once a week watering would the nutrients perhaps become deficient before the water has been used?

Gravel top dressed with clay.

yeah smarty, never thought of that until you showed it.......great idea in lowering costings....creedo's to you on that one Duff

Using "unfiltered" AP water... and the nature of coir... I'd suspect that a degree of solids would be retained within the coir with each watering... and kind of act as a "slow release" fertiliser... along with any breakdown of the coir itself...

A lot of coir products have been soaked in sea water... and probably retain a degree of trace elements from that alone...

Personally... I've abandoned coir as a media.... in hot climates, it may have a place though...

Good point, the setup I am trying uses sump water so solids are not so obvious