Questions on Hydroponic Growing

Hello all!

New here and about to start my first grow. I did have some questions I’m hoping you guys would be able to help out and I’ll include as much detail as I can about what I have.

I’m about to start germinating my seeds and will be growing hydroponically in Promix HP.

I’ll start out in a solo cup then transfer to 5 gallon cloth pots I have.

I’ve read that once planted in the promix HP inert medium that I should water it with nutrients at seedling or 1/4 strength. Can anyone let me know their thoughts and experience on this point?

In terms of transplanting, after about 14 days in the solo cup, I’ll get that done. I had read it’s important to make sure the medium is moist in the new larger pot so I should water before and right after transplant. Is this accurate and should I water with nutrients right after or just water?

I had also read that before adjusting nutrients, it’s important to do a flush once in veg/bloom. My question here is, once you flush, how soon after do you water again with the new nutrients? Do you treat as you would when watering with nutrients? i.e. wait till it feels dry then water with nutrients? I read this part here to water as needed.

Finally, I know, based on what I’ve read on these forums, that there is no set watering schedule, you do as needed by feeling the medium, but as a rule of thumb for 5 gallon pots, how often have you guys needed to water in your experience?

Here is what I’m using:

  1. Blue cookie seeds
  2. Nutrients:
  1. 36"x36"x72"grow tent

  2. Horticulture Lighting Group 260 Watt V2 RSpec Quantum Board DIY Kit (Full-Cycle)

Let me know if you need more infos and thank you in advance for your help!

Growing in 5 gallon fabric pot filled with promix isn’t necessarily hydroponics. Are you planning flood system or something? Otherwise we would typically just call this a soilless media.

As far as seedlings go, the cotyledons will provide just about everything plant needs until they start to yellow. Most will whip up a little concoction though, just to keep media charged and maybe get some rooting supplements in. Exact strength probably depends some on what you plan on using.

I see myfriendis410 posting, he is great grower that uses promix, so I will defer to him on the rest.


Yeah you’re right, soilless media is the right terminology. As it’s my first grow and I’ve already invested a bit into it, I wanna avoid spending too much more money just yet until I do a few grows and really learn as much as I can. So no flood system or reservoir for now.

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This is not hydroponic but rather soilless. Promix HP is a great medium and my personal favorite.

Seed germination: coffee mug with 1/4 cup of distilled or R/O water and 1/2 tsp 3% peroxide. Immerse seed and place in a warm dim space until seed shows a tail.

Plant in Solo cup (poked full of holes) with media slightly dampened. This can’t be over-emphasized: you want almost NO moisture around sprout. The best method is to dome sprout with a clear Solo cup and mist inside of dome twice a day with a spray atomizer of distilled or R/O water. No need to PH it.

Do this with no nutes for 12 to 14 days under 24/0 light schedule. Watch the first round leaves (cotyledons) and when they yellow it’s time to start feeding.

You can transplant at this point and as the plant gets larger your watering amount will go up. Let the plant tell you. Eventually the plant will put out roots into the medium and occupy all of it and drink a gallon or more a day. But not now. Too wet and the sprout will die.

The only way to be successful with Promix is to have good equipment. The HLG light is great and you need to match that with a good PH and TDS meter for when you supplement.

If using FF nutes then yes per their grow schedule.

Once you supplement the plant you need to be on a schedule and feed on alternate days. So, feed/water/feed/water. You can increase the solution strength of your medium by changing that (if plant is hungry) to more frequent feeding: f/f/f/w/f/f/f/w for example.

Keep nutrient load at or below 750 ppm in veg and around 900 in flower, unless plant tells you differently. I see you are using AN PH perfect: lots of growers having trouble with this product line. Would be a better choice to use “Jack’s 3-2-1”.

High efficacy lights tend to make plants calcium and magnesium hungry so need to supplement additional nutes with cal mag. Follow package instruction.

Soilless media needs to be watered daily.


410 this is awesome and more than I would have expected. Thank you!

Glad you said this, I did a lot of research and that seemed like the best option to me.

Distilled water is easy to find in pharmacies here so will definitely be grabbing some.

Some follow up questions: slightly dampened. So let’s say I use those classic red beer pong cups, fill it half to 3/4 with the promix HP to put the seed in. How many ml of water? when you say sightly I think 50 to 100 ml, if not less.

I have a bit of a worry with the size of the cloth pots I got, is 5 gallons too big for when I transplant or does it simply mean I don’t need to water as often?

That’s good to know, thanks for the advice. I’m gonna try it out for this first grow since i already paid for it but I will keep Jack’s 3-2-1 in mind for the next one. What kind of difficulty to growers find with it? Getting the PH and EC right? Do you have any tips for using this?

It seemed like the best option, pricey but worth in the investment I hope. One question, this light came with a dimmer, the tent is 6ft high and it hangs pretty high up, I’d say 24 to 30 inches away from the seedlings once in there. Would you put this on full blast? I had read technically they don’t even need this light but it’s good to have it while so it’s available for when they do.

Last question for the moment! at what point do I switch to an 18/6 schedule? Do I do it gradually or just switch to that as soon as I transplant and start veg?

Thanks again!

I should ask, does it mean I need to water with and without nutes in larger amounts daily?

Take a fist full of Promix and wet it thoroughly. Then squeeze as much of the water out as you can. That should do it. From there you will add water in ml: better is to just mist the clear dome twice a day. The idea is you want to promote root growth and when a sprout it derives all of it’s moisture from the air as there is no taproot.

Once plant is established you can go into final pot. I use an intermediate 1 gallon plastic pot but I do photoperiod plants; you can handle them more.

My understanding of AN PH Perfect is to not worry about adjusting PH. You would have to do a search of others using it to find the problems.

I would run light 24" above sprouts and turned all the way down. I use high efficacy diodes and have never had to turn them all the way up. Those Samsung diodes are most efficient at about 70% of peak.

You can just adopt an 18/6 schedule when you transplant. Frankly I would do 16/8 using those lights.

Thanks again for all this!

So would keeping the tent generally quite humid a good idea in this phase? I did read the grow journal on this site and found the plants were kept quite humid gradually decreasing as we enter bloom, at 50% as the lowest.

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We generally recommend putting a dome over the seedling to maintain as close to 100% as possible during the first two weeks.

Got it, thanks :slight_smile:

Hello again!

So the seeds are well on their way, gonna plant them in the next few days.

I had one more question: I know how often to water now, but once transplanted, how much water do I start with? is there a rule of thumb to follow?

I’ve read something about the size of the plant, 1/2 gallon for 2 feet tall etc. Any insight on this one.