Clean-up and Nutrient Change

Not much to report, but I'll go into a lot of detail anyway. I'm bored.

I finally got a pH pen which will have to hold me over until I can get another monitor. Even with the monitor, it's still useful because it lets me see the pH in the rockwool (what the plants see) as well as in the reservoir. I can't measure EC, but mixing the nutrients as instructed by the mfr will get me close enough. And no, it's not a crappy Hanna! (It's a Eutech)

I'm out of distilled water, so using tap water (non chlorinated, thankfully). I know it's about 300ppm (though not sure what's in it - need to request a water analysis), hopefully that doesn't cause any problems.

The ugly fulsium wilt like symptoms are gone, but there are some light spots on the leaves that look like a nutrient deficiency.

This pH pen showed me something very interesting - pH coming out of the drip stakes was 5.7, but draining back into the reservoir (after going through the (previously soaked/leached) rockwool cubes and the cocotek mat (not previously rinsed) showed the pH at 6.3(!). My best guess is that the coco mat was a relatively high pH... probably neutral (7.0), and this was causing some nutrient lockout problems.

I have added 10ml/gal of 35% H202 and cycled/flushed the system with fresh pH adjusted (5.9) water for an hour. That should kill most of the cooties that may have still been lurking in the system. I am next (in the middle of it now), draining this water to make sure cooties are actually removed from the system as well as removing any pH imbalance/buffering crud. Note that keeping this level of H2O2 in the system for any length of time (a day or more?) can kill your plants. Always pre-mix 35% H2O2 with a good amount of water. It is caustic and should be treated as an acid. This is not the water-like drugstore stuff!

The plants are growing so fast and seem nutrient deprived, so even though it's only been a 10 days, not 2 weeks, I'm jumping right to the "3rd+ week vegetative" nutrient levels. I'll be adding the Super B+, but not using any more Royal Gold (fulvic acid) until the plants start to set fruit - the Royal Gold is too expensive to use haphazardly.. and these are tomatoes, not basil, saffron, or some other high value crop. The expense isn't justified.

To this, I'll be adding 2ml/gal of 35% H2O2. This small amount will help keep molds, fungi, etc. out of the system as well as provide additional oxygen to the plants. The oxygen giving effects of H2O2 lasts about 4 days. I'm not that concerned about this benefit as I always aerate the hell out of the reservoir. I'll thrown in another 10ml (total for 20gals) every 5 days or so whenever I add water to the system.

Lastly, a few plants have gotten big enough that the roots have taken hold in the rockwool cubes. I have tied the twine to the top bars in the tent for these plants and started training them to the twine.

Final measurements were:
Water: 22 gallons (nutrients measured for 20gals to allow for evaporation/transpiration)
Micro "Bang" P (Add 1st): 95ml
Grow "Bing" N (Add 2nd): 190ml
Bloom K (Add 3rd): 57ml
Super B+: 75ml
H2O2: 25ml
pH Down: 40ml

Final pH measurement: 6.0
This is the low end of what the mfr recommends (6.0-6.5) during the vegetative cycle. Optimal nutrient uptake range for a plant is 5.7-6.3 or thereabouts. Since the mfr recommends 5.6-6.1 during the bloom stage, I'm staying at the low end during the vegetative stage to avoid stress to the plants when going from vegetative to flowering/bloom nutrient ratios.

Always dilute, here's how I do it, and the order I do it in:
- Drain reservoir. Flush with 10 gals pH adjusted (important!) water if desired. I usually do this every other nutrient change. This removes built-up nutrient salts, cleans out a lot of crud (fungi, loose bits of rockwool, etc), and helps prevent lock-up.
- Add 5 gals water
- Add Grow (N)
- Pull drain stand-offs so all liquids drain immediately back into reservoir and don't get absorbed (much) by rockwool.
- turn air and big/flood water pump on to start circulating/mixing
- Add 5 gals water
- Add Micro (P)
- Add 5 gals water
- Add Bloom (K)
- Add 5 gals water
- Add Super B+
- Add H2O2
- Add final 2 gals water
- Let circulate 5 mins
- Take pH reading. Add pH adjustment (almost always 'pH Down') 20ml at a time.
- Allow 2 minutes of circulation/mixing between additional pH readings
- Repeat last 2 steps until pH is at optimal level
- Turn off big/flood water pump, put drain standoffs back in.
- Turn on drip pump for 5 minutes to get a little nutrient back into the rockwool. Do NOT walk away at this point. I have nearly killed plants on 3-4 different occasions by doing this and discovering 24-48 hours later that the poor things had a non-stop flow of water and nutrients all that time.
- Put drip pump back on timer. Close-up the tent, clean up. Grab a beer.

Note that if you did flush the system, the rockwool will have been extremely saturated for some length of time. Expect the plants to show mild symptoms of over-watering for a day or so. When they are really young (like now), I'll go so far as to skip the next timed watering and set an alarm on my calendar to put that cycle (in this case, midnight) back on the timer the next day.