Hydroponics Greenhouse

Hydroton Problem History

I have approx. 8 ý cu. Ft. of Hydroton in each of two beds. Each bed has a surface area of about 12 ý sq. ft. The nutrient solution reservoir holds about 200 US gal. The beds are fed in parallel.

The system has been down for about 3 years. The Hydroton was purchased 3 years ago and has been stored in the original sacks in a dry location.

I decided to flush the system with bleach (Sodium Hypochlorite). I added 192 oz of common household bleach to the reservoir and pumped continuously. (The beds are fed from below. They overflow into channels that returns the solution to the reservoir.) The reservoir is made up of five 55 gal. Plastic drums, connected in series. The pump is in the drum at one end of the string, the overflows both go to the drum at the opposite end of the string.

A peristaltic pump can inject sulfuric acid into the drum that contains the nutrient solution pump. (The acid is battery acid, purchased from an auto parts store and diluted 20:1.)

The tap water is from the Rogue River and is typically about pH 7.2. Analyses show that there is very little of anything in it.

Shortly after adding the bleach the pH went to about 12.7. (The pH electrode is in the drum that receives the overflow.) After circulating this solution for about 2 days I dumped it and refilled the reservoir with tap water.

I have been pumping (recirculating) continuously for about 4 days. Over these 4 days I have added approx. 2 gallons of the dilute sulfuric acid solution. The solution has finally come down to pH 6.7 in the tank that receives the overflow. The solution, at entry to the beds, is about pH 6.0.

All of my previous experience has been with using pea gravel in the planting beds. Is this (as described above) typical for Hydroton?

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