Shells in creek gravel

[jim mckee]

Howdy

I'm looking at using some local creek gravel for grow bed media.  It has some small shells (.5" dia max, scallop shell shaped).  These shells are bound to get ground up with grow bed usage and make small changes to the water.  What will shell material (I'm guessing mostly calcium) do to water specs?

The local creek gravel contains no lime stone.

Tanks.

jim

[Vlad Jovanovic]

The shell material (calcium carbonate) will act as a pH buffer. Which can be a good thing, or can be a bad thing. That depends on a few other things like you source water parameters. And the amount of those shells present. (% -wise of total media volume). Say, for instance your waters kH (carbonate hardness) is pretty low (soft aggressive water) and you have a total of...oh IDK 10-20% shells in there, that would be a good thing. Adding some stability (pH wise) to your system.

On the other hand...if your source water has a very high kH value ('hard' high pH water) and you have a bunch of shells as a significant portion of your media...that would be "bad". Likely you would have a pretty high pH that would be tough to lower without resorting to collecting rain water for top-ups, acid treating etc...(but even then it would probably be tough to maintain a pH below 7.6 or so until the buffering capacity of your media gets used up). Hope that helps somewhat... 

[jim mckee]

Vlad

Thanks, good explanation.

We have well water that is soft water low pH and I'd say the shell ratio is 5%.  Also about 5% petrified (?)  reeds or what look like a section of a spinal collum, I'd guess it was aquatic plant  that's now petrified or mud got into the hollow middle of a reed like plant and hardened. 

The gravel looks like terracotta and contains finings that look like clay mud .

I'm on the fence about how much finings to rinse out.

The clay finings or mud makes the water a little brown clowdy.

Anyone have an idea?

I'll be raising Tilipia, 2ea 250gl tanks,  300gl grow beds and about 100' of 4" pvc growing lettuce.

Will Tilipia remove the fine clay material through their gill feeding or is the material too large (eventhough it's pert-near microscopic to me).

I think I'll use an ultra fine cloth filter also as it may take a long time to remove the clay and I think the type of gravel is pressure hardend clay (it's all the same color) and grinding the material around because of the gardening aspect will cause the material to give off small amounts of fining.

Tanks

jim

[Vlad Jovanovic]

jim, if I'm understanding you correctly...It'd be a real good idea to wash out as much of the fine particulate matter as possible. I know that washing media can be a huge pain in the ass (or lower back really), but it seems like those that have skipped on the media rinsing have regretted it in one way or another...Not so much because of any discoloration, but because of the other problems having lots of fine sediment poses. I had to triple rinse 8 IBC tote beds worth of media, it's not much fun but I'm glad I did it...and it's something you really only have to do once, so it's not so bad.

If by 4" pvc growing lettuce you mean a homespun NFT rig (I'm pretty sure that's the case) you will also need to plan for a way to remove fine particulate (fish poop and other small solids) organic matter. Without some sort of additional fines filtering plant roots in an organic hydro/bio-ponic/AP system tend to get "gunked up". And it pretty much sucks when that happens. Things work well at the beginning though, but get crappy pretty quick (relatively speaking) so plan for that. It doesn't have to be a "fancy" fines filter or anything...just some way to trap and remove them...A media bed can only get you so far. Hydroponic NFT with mineral salts as nutrient input doesn't have that problem, but with AP you can count on it.

Sounds like those shells may somewhat help save you the hassle of having to buffer as frequently, once nitrification really kicks in. With a soft aggressive source water though, plan on having some builders lime (calcium hydroxide) on hand in the shed... just in case (so's that you can keep your bio-filter from potentially crashing). Potassium bicarbonate is a wonderful buffer to have on hand as well (wine making supply shop or e-bay). You can alternate between the two...KOH is an alternative potassium buffer, but is quite strong, which isn't a problem or anything...just be careful not to over-do-it is all.

jim, why tilapia in Tennessee? I mean why not go with a more climate appropriate and/or local fish and forever save yourself tons on heating and electricity?

[jim mckee]

Howdy

Thanks for the info.

 

Why tilapia because of energy requirements:

I sawmill /kiln dry and manifacture flooring to fine furniture. I use my scraps to run a hydronic heat system for the kiln/shop/house.

Were setting up a wood gas gasifier to run an engine/generator.  We'll use the scrap heat from the gasifier to heat the greenhouse.

My gh is on the south facing wall of a bldg.  The wall is the wall of a lumber drying kiln so it is insulated with 12" of Styrofoam so I get one heat loss free wall.  If the kiln is running I can vent the warm moist air into the gh also.

So I have a good heat source and electric source.

 

I can't wait till ordering time for Red claw crawfish  http://farmingcrawfish.com/

Tanks

jim