Backyard Aquaponics
A place to discuss aquaponics

I have crushed coral buffering my system. Available through aquarium supply stores. The guy at the store told me the pH would spike to 8.0, but I'm maintaining a very steady 7.2 with 28 pounds in my 120 gallon setup. Go figure. Do you have a discount aquarium supply somewhere close?

I collected a bucket of shells from the beach last time we were there. I will just mash them up a bit and use them in my next grow bed.

Whatever you decide to use, add gradually until you see how it affects things. pH spikes are bad for fishies.

how dose the shells adjust the ph? i have fairly hard water too, dosn't that mean it will resist ph change? what dose most peoples nitrate levels stay at? where should i be for optimal results

Rb, its been covered in depth in a PH thread, but as i know how hard it can be to find stuff i'll go over it lightly. Do look for the thread though, LOTS of techi info there.

the shell grit is calcium carbonate which is normally not very soluble in water. as the ph shifts down the acids attack the carbonate and are neutralised. Happen on a continuous basis, and i have never seen any of my 4 fish tanks go above around 7.6 or below 7.4 using the shell grit.

The chemical process is much more involved, including reversable reactions with dissolved carbon dioxide, but the little description above should give you the drift.

RE: nitrates, after playing a little, reading alot about others systems, and using some of my perch as test subjects i'd settle for 20 to 60 ppm

ok kool kool im about there with the nitrate hopefully it stays! im just gonna put the shells in the seperate filter i have built u think that will be ok?

should be fine, asl long as the water flows over it.

Hardness is not quite the same as alkalinity (can't remember the difference). Alkalinity is the buffering capacity of the water. adding CaCO3 provides a source of buffering capacity. I expect CaSO4 (gypsum/plaster of paris) would be effective as a buffer too?

Don't think hardness was mentioned, but yes, they are different, as the calcium carbonate is "used up" the hardness (both KH and GH will rise)

Not sure if it will actually register a high alkilinity, as most of the buffer exists in non-dissolved form, maaintaining equilibrium.
Now, the Rise in KH and GH as the calcium carbonate buffer is at work may indicate that you will end up with an ultra high hardness i your tank, but as many plants will take up calcium (turnip greens have 250mg per cup cooked vegetable) then i think we may happily use this buffer, without the detriment of the sodium in commonly used bi-carb and even give our veggies a source of calcium!

happy buffering

For those that are interested i believe there is info in the "useful info" section"

Caso4 i don't think so, buffers are GENERALLY carbonate or bi-carbonate based (yes i know of the acid/acid salt mixture buffers). it will however raise you general hardness (GH)

On the nitrate. I've had it up to 600 ppm. The plant growth was 2 1/2 feet in 2 weeks (hyphenated tomatoes).

This was too high I figured, tough fish though for the mad experiments (goldfish). Did a 50% water change to reduce it to approx 300 ppm and doubled the plants in system. Growth didn't slow down at 300 ppm nor did it slow down at 150 ppm.

my fish stopped feeding at around 300ppm

My water is also very hard, but has very little buffering. Adding the coral raised both of those readings a tiny bit. My tap water is 6.4 pH (or less--that's as low as my tests go) However, my pH stays very steady at 7.2 in the system now.

have observed the same, the goldies don't seem to worry too much about nitrate levels yet the SP stop eating near 300 (trying to keep it below 150(and balanced)) - don't you just love HSM!

so i got home from work today any my nitrate level is 0, i added 20 goldfish today too making the total count 60, any thoughts how i can bring it back up? i just fed them a bunch so ill check the levels in a couple of hrs

Tell us more about what you have in terms of plants.

ive got 2 medium tomatos and 2 slightly smaller peppers, the toms have lil tomatos goin but the peppers don't, then i have a smaller bed that has alot of lil seedlings lettuce chilies and some flowers just kinda threw them in some have sprouted

Toms and peppers (as you call them) will use a lot of nutes, particularly when forming fruit. I had one massive tom that pulled enough nutes out of my system to support my 30 largish perch. I guess the goldies may not be up to it. Monitor it for a bit cause it will take some time for the nitrate to register if the 20 new ones have made a difference for you and the plants use slightly less nitrate than is now produced. One thing would seem to be likely though, as your plants get bigger you are going to have a nute deficiency in this system.