Newb here.. So, I purchased this grow box: Yield Machine Max LED Hydroponic Grow Box | Grow Cabinets It came with a basin that holds about 3.5 gallons when filled to the appropriate level, and it came with the General Hydroponics Flora series of grow, micro, and bloom. Now here's my question/confusion-- the vendor states in the instructions : Liquid Nutrient Plan 1 teaspoon of grow half teaspoon of micro. Mix both into a gallon of water, this will be your nutrient mix. Use this once per week pouring a quarter cup from gallon into water filled basin. We usually do this after a weekly water change. So mix up a gallon of nutrient mix, and then basically add 1/4 cup per week to the approximately 3.5 gallons of fresh water in the DWC basin. Where I am confused is that this seems to be *a lot* less than what is marked on the bottles, and a lot less than what I am reading online. Using RO water, 1/4 cup of this solution basically gives me a TDS of 50 in my basin when mixed with water. Everything I'm reading says I want a TDS of 600 or so. As instructed, a gallon of that nute mix will last for 64 feedings/water changes, and that's only using a teaspoon of Floragrow! I called the vendor and he doubled confirmed this-- even told me that if I add more than a 1/4 cup I risk killing the plants. I have been running using the provided instructions since the start of my grow 3 weeks ago, and my plants are about 4 inches tall with 10 leaves or so and look healthy so I'm loathe to change anything, but the way I'm currently running doesn't seem to jive with anything I'm reading online. At the provided measurements, a single bottle of floragrow is going to last me literally forever.
Most nute companies (especially GH in my experience) recommend too much nutes, and many of us use 1/4 to 1/2 of their week-by-week recommendations. But a ppm of 50 for a 3 week old plant seems much too little. You might get lots of different opinions, but if this were my Deep Water Culture plant, I'd slowly increase to 1/4 of what GH recommends, and see how the plants respond. Be on the lookout for yellowing/clawing leaf tips, typically a sign of overfeeding. That your plants "look healthy" is a sign that you're doing something right. Too little fertilizer will lead to shorter plants, too much can lead to plant death. You might eventually have a height problem, and might need a plan about what to do. Maybe the sparse nutes are recommended to prevent that.
Thanks for the feedback. I will do a basin water change tonight and up the nute dosage and see what happens. Just find it mystifying the discrepancy between the instructions and nutrient levels on the web. The vendor swears that if I were to add more than 1/4 cup of solution I risk killing the plants, but if that was the case everybody here would have dead plants. A gallon solution containing 1 teaspoon of nutes, of which only 1/4 cup is added to 3.5 gallons of water, is TINY in comparison to what people seem to be dosing.
But be very careful. The vendor might know something about the setup that we don't. My first thought was that the vendor was telling you to use 50 ppm FOR SEEDLINGS ONLY, and that he might recommend upping the nutes as the plant gets bigger.
So these plants right here are getting just barely above the seedling dose per the GH Trio feedchart. GH says to use 1.25ml/gal for seedlings. I am using 1.75ml/gal which gets me around 350ppm. Above 400ppm they throw brown tips and look like shit.
Redid my reservoir last week with more nutes, about 1/4 dosage listed on the bottles. Got an immediate burst in growth for a few days, then they stopped and now one of the two plants has developed a brownish/grey mottling on the lower leaves. Looks like phosphorus deficiency to me so I added more Bloom yesterday however the greyish cancer is still slowly progressing on that same plant as of today. PH also dropped from like 5.8 to 5.3 in 24 hrs, which I have readjusted back to 5.8. What's weird is that despite the mottling existing on every lower leaf on one plant (and has slightly spread to a few upper leaves) the other plant is totally unaffected except for a few tiny spots. The unaffected plant is slightly larger and more mature than the sick one. Roots of both plants are as white as the driven snow too. EDIT: TDS meter is 3 digits with no decimal places
Ppm goes down, plant is eating nutes. Ppm goes up, plant is drinking water. Ideally it should stay about the same, if I remember correctly.
I totally flushed the basin and redid the nutes with CalMag as well as some bloom nutes, as the brownish cancer on the lower leaves sure looked like phosphorus deficiency to me, and grow/micro have very little phosphorus (I was only dosing micro/grow previously). It's been a few days and new growth appears unaffected, but the leaves that were effected continue to worsen (spots spreading on leaf). I'll probably have to wait a few more days to see if it's cured, as the spots start on the bottom leaves and spread up, so new growth is unaffected at the start anyways. The healthier of the two is chugging along with only a few random spots on bottom fan leaves, the smaller one I just finished cutting all the unhealthy leaves off of, so I'll have to wait and see. They are WW autoflowers so my main concern at this point is stunted growth/yield-- they are already in pre-bloom and the smaller plant is probably only 6" tall lol while the bigger one is only 8", but is phat like a bush. This is my first grow so obviously a learning experience. Ironically I have a masters in chemistry so there is some irony here.