PH fluctuating quickly

[duanes]

Crushed Oyster shell is inexpensive, aragonite can be pricey, but both do the same thing. The acids that lower pH leach calcium from each.
In the states, beside mixed in with substrate, I used fine grain aragonite as media in a fluidized bed reactor. After a few months I would add a litte more to keep pace with the amount that had been used up by metabolism (acids).


The reactor held about 5lbs of aragonite and stood about 4ft high, 8" in diameter.
After adding new aragonite, the water in the tanks would sometimes get a bit milky (seen in the last pic), the reactor covered a line of 4 or 5 tanks, on the barrel sump, in total equaling about 300-400 gallons.

 

[Ulu]

What was the approximate flow thru the sand filter?

The small one I have doesn't move over ~30 gph without spitting sand into my sump.

I am planning a large one.

 

[duanes]

The filter is about 4 ft tall, 6"-8"in diameter (don't remember exactly), sand gets agitated to about the 3 ft mark.

 

[Ulu]

I was using aragonite, and some shells, but now understand the oyster shell will buffer to a higher pH than aragonite.
OTOH, I feel aragonite works far faster, but that might have everything to do with the size of particles which is about 100x larger for the crushed shells.

 

[duanes]

I couldn't be sure about flow rate, it was a 1200 GPH pump split 4 ways (3 tanks and the fluidized bed), and I used a ball valve to adjust flow thru the reactor just enough to move aragonite, to the @ 3 ft mark, basically eye balling.