Backyard Aquaponics
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I live on an island that is 99% limestone. I was wondering if I could use limestone aggregate as a grow medium. The reason for this is that it would keep the Ph levels between 7.0 to 7.5 from what i have read and it would also help as a biofliter. If 100% limestone is not advisable then what about 50/50 limestone and expanded clay.

Thank You
Richard

I doubt it would buffer your system that low, I'd be thinking 8-9 will be more like it.
We generally advise against limestone, as fish may enjoy higher pH, but most plants wont
Sorry to make it difficult for you.

I would suggest looking into coco peat and seeing if you have any inert rock about. As you live where you do it may be difficult to find rock, but coco peat should be easy.
Do you have any ugly beaches with pebbly sand (I doubt it but...)

I really don't know too much about Tinian unfortunately. You're rather far north, a touch farther north than bangkok right? So I'd expect lovely white sandy beaches and coconut palms. If you're on a bed of limestone you unlucky. Beach rock is about your only hope I fear.

Limestone probably will buffer higher than you would like. My guess is it will tend to a pH of 8. It might be worth testing some of the aggregate you are thinking about using. Soak it in some distilled water for several days and then test the pH of the water.

What about Washed Sea shells? My AP system has lots of washed shells in it (not quite half of my media, the other half is pH neutral media) and my pH tends to buffer to 7.6.

the coir might also be a useful option for you.

Ditto... limestone will result in a pH of 8.0, or worse...

Not only will this affect plant growth, but it will make cycling and maintaining your bacteria colony difficult....

Your saving grace, is the temperatures you're likely to get in your area...

So what pH level would benefit both plant and fish. I have just read "The Nitrogen Cycle" by Steve Cacchione BYAP Issue 1 Summer 2007. He suggested that limestone could be used to maintain a pH of 7.0 to 7.2 and that it will stop dissolving at a pH of 7.4.

Water test sample from our utility company shows we have hard water.

If I can't use limestone aggregate then I will need to find another alternative for a grow medium. Importing expanded clay will cost me an arm, a leg and one big toe.

Thank you very much for replying to my post.

Temperture during the day 84 to 96 degrees, and at night 76 to 82 degrees roughly. We have typhoon, dry and rainy seasons.

I noticed that there had been volcanic activity in the Mariana Islands, have you examined the possibility of volcanic rock? I also see there is a fair amount of construction (concrete work going on) what are they using for aggregate?
Think what Steve was talking about was using a small amount of limestone as a buffer against ph falling, as many systems trend towards lower ph.

Sorry I tend to look at subjects not people, welcome.

It depends on the limestone too and what else is in the aggregate. Being that you're on an island, seashells, or shellgrit would be your best pH buffer, but as a media, I fear the pH will be too high. 6.6 - 7.0 is ideal, but mos of us run at 7.4

Thank you for all the replies. We use limestone for all concrete constructions here. All of the construction companies here make there own limestone aggregate which they sale to the public. They don't add anything to it until they mix it with concrete.

Islands with volcanic activity is off limits and those that are not active are wildlife preserves.

I will try putting the aggregate in distilled water and check the pH after a couple of days and see.

Just priced out a 50 liter bag of hydroton plus S/H and it will cost me around $120.00 per bag.

Once again thank you for your replies

i think oxygenating the water will prove a better test.

hey siricktiq

i know this is an old thread...did you have any luck sourcing other rock, or did you use the limestone? Im in a similar situation as you..