We started our system in November. The plants have been thriving up until recently when we began noticing brown spots on many of the tomato leaves (see attached images).
We have been conducting water tests regularly and the most recent tests yielded the following results:
Ph- Test stip=6.8 Drop test=8.2
(This brings up another issue...the water test strips always give a different result than the water drop test. Does someone find one more accurate than the other? Let us know)...
Ammonia- .25ppm
Nitrites- 0
Nitrates- 10ppm
Our teacher theorized that the problem could be a result of a potassium and/or phosphate deficiency. If someone believes that this is in fact the problem, do you have a suggestion for what we can do to raise the levels?
We currently have 1 tilapia in the system but will be adding 4 more later this week.