down here we use black cinder, also known as scoria or lava rock. its light, porous and cheap. I can get it by the truckload for $103 or by the 3/4 cubic foot bag for $4.28
Ya that happens. It will clear up. 8.3ph seems a little high for coco coir tho. did you measure the ph of water before you added it?
Actually, my ph was a bit low in the water, and marble chips helped raise it a bit. I will keep tabs on the ph and let you know if ph gets too high
coming across some conflict in medium when it come to gravel ... limestone and marble a no no ... but granite is recommended by most but some say it changes the ph ??
Most aquaponic home gardeners are using media based, flood and drain systems. A media based grow bed optimally has about 12” of either ½ – ¾” gravel (no limestone or granite!)"
Some clarification would be appreciated
I've been using 1/2" brown river rock successfully for a few years now. I have also used shells in one system which keeps the pH quite high which I don't really recommend unless your primary goal is going to be to grow watercress along with your fish. Anyway, I would call 1/2" the small side of acceptable media and there are many who will recommend 3/4" media but it may be harder to find. 3/4" will allow more air space between rocks and will be slower to clog but 1/2" will also work as long as you don't overburden your system and beware of aggressive plants that tend to take over the world and clog growbeds with their roots (banana, mint.)
Whatever your media, I recommend getting a sample of it to run some tests on before you go buying a large amount. Most media also needs washing before you use it or you many experience some temporary (3-6 months or more) pH elevation from the dust on/in the gravel. Just because a particular media might be inert, it doesn't mean that the dust that might be all over it is safe. Lava rock sitting next to a crusher machine breaking up concrete and limestone for use in roads is going to pick up a lot of limestone dust which will affect pH if not washed out well. Also, many of the expanded clay, shale products may need an initial rinse to get rid of oxides that can affect pH initially.
Anyway, run some tests, don't just assume that "pea gravel" is going to be fine for you just because someone in another part of the country says they use "pea gravel" (pea gravel describes the shape, not necessarily the type of stone, here in FL if you call a supplier and just ask for a truck load of pea gravel it's going to be limestone.) One test you can do is to rinse the media well and then drop a hand full in a cup of vinegar. If it fizzes, then it will probably keep your pH too high.
Media I've heard of people using
River rock (mostly quartz type rocks)
Lava rock, pumice, scoria
The last two choices are manufactured from natural mined materials by heating it.(shale/clay)
I'm interested in what you say about river rock and lava rock. Because Hydroton is small it takes a lot of it to fill the IBCs and, as you say, it becomes expensive. Home Depot carries both lava rock and a decorative river rock. Would both --either? -- work for the grow beds if I fill the top two inches with hydroton? I don't have easy access here in the Keys to large amounts of either but then I'm only filling three IBC beds.
Michael, if you have a truck, (or a buddy with a truck) you might want to go get your river rock or lava rock from the Conrad Yelvington yard up in Miami. Filling an IBC with bagged rock is gonna cost a lot!!!