Pretty good a customer service at Fox Farms...

I wrote them this afternoon with your basic background, where our plants were from (acidic Indonesian soil) and your desire to keep the ph down. Hopefully it helps, but here's the reply e-mail I just recieved:

Hello Rusty,

It sounds like you guys have a good grasp on the principles of soil science and indoor gardening. Hopefully I can add a few pieces of information, both practical and technical, that will help find answer to the underlying questions in your e-mail. The first area of concern is testing the soil pH.
Ocean Forest is pH buffered with oyster shell to be in the 6.3 to 6.8 pH range. The most reliable method for home gardeners to test their soil pH is to gather some samples from different plants, at different depths in the soil; mix the soil with an equal amount of purified water; let stand for an hour and test with a digital pen. Most soil probes, for pH or moisture, are very inaccurate and unreliable. I would not give a soil probe reading much value.
So, the initial soil pH is going to be in the previously mentioned range. The pH can change upwards or downwards over time due to several factors which may or may not come into play. Acidification can be caused by the degradation of peat, the accumulation of acidifying salts, rapid microbial activity, and the loss of buffering capacity. A rise in soil pH is usually associated with water quality; water hardness and alkalinity can build up over time, even with the application of nutrient solutions at the proper pH range. Salts can raise or lower the pH of the soil depending on the selective uptake of plants. Carbonate Ions in the tap water (well water also) can buffer acidity and build up in the soil, raising the pH of the soil over time. Oyster Shell is also mainly carbonate atoms, and will buffer any acidity as long as is stays in the soil. This website has some great in-depth resources on soil chemistry and pH:

SSC 102 Soil Chemistry

Plants that evolve in acidic soils have adapted their diet to be demanding of Iron (available) and sensitive to Phosphorous (un-available). This is because of the inherent availability and un-availability of those nutrients at low pH ranges, and those plants will be angry if Phosphorous is applied heavily, or the soil pH is too high. Most plants have evolved to grow in slightly acidic soils (6.5) where nutrient availability is generalized.
I hope this information is useful and helps explain our products and the pH regulating activities used by gardeners. Let me know if you have any more questions about this or any other topic. Good Luck!


Joe Alcorn
Customer Service & Technical Support
P.O. Box 787
Arcata, CA 95518
(707)-443-4369 main
(707)-269-4458 fax
[email protected]

Crap. I ammend my water ph with phosphoric acid. Guess it's something I'll need to keep an eye on.
Anyway...I hope this is as useful to you as it is for me. I'll take a look at his provided link in a bit. Time for some Ding Dongs and a soda.