Cost of nutrition upkeep in RDWC

[king_of_nothing]

Hey guys,

I am currently in the middle of engineering a some what large RDWC system for a first growers adventure and I want to make grateful use of all of the existing information on the web on the matter.

So I was calculating the upkeep and I got pretty concerned with the nutrition requirements for a RDWC. But perhaps my reasoning is off somewhere.

This post is actually a deep copy from another post of mine in a different thread (link here) on thcfarmer.

So I am thinking of two 1200 L (317 US G) RDWC installations for flowering. and one 700 L (185 US G) set up for vegetative. I got the airflow and waterflow and water temperature covered. So for my own system as starters I was thinking of using the General Hydroponics Flora trio nutrition solution to keep things simple and maybe later mix my own micro/macro solutions. However if I am looking at GH's flora's suggested feeding schedule for recirculating systems (link here) you need in the order of 20 ml / Gallon in res of averaged nutrition solution a week. So that translate to (2*317+185) * 20ml /G ≈ 16.4L of nutrition product every week! In my own euro country, I can buy this stuff at about 17.50 euro a litre. So this would mean that I require roughly 290 euro's worth of nutrition every week. Which feels like a lot! Sure, I can try to buy this stuff in bulk overseas to get it more cheaper. But even if I could get it at half the price, it still feels very expensive.

Is my reasoning very wrong here or are other RDWC growers also adding roughly 20 ml of pretty expensive stuff for each Gallon in there system as well?

Thanks people!

 

[Aqua Man]

Hey guys,

I am currently in the middle of engineering a some what large RDWC system for a first growers adventure and I want to make grateful use of all of the existing information on the web on the matter.

So I was calculating the upkeep and I got pretty concerned with the nutrition requirements for a RDWC. But perhaps my reasoning is off somewhere.

This post is actually a deep copy from another post of mine in a different thread (link here) on thcfarmer.

So I am thinking of two 1200 L (317 US G) RDWC installations for flowering. and one 700 L (185 US G) set up for vegetative. I got the airflow and waterflow and water temperature covered. So for my own system as starters I was thinking of using the General Hydroponics Flora trio nutrition solution to keep things simple and maybe later mix my own micro/macro solutions. However if I am looking at GH's flora's suggested feeding schedule for recirculating systems (link here) you need in the order of 20 ml / Gallon in res of averaged nutrition solution a week. So that translate to (2*317+185) * 20ml /G ≈ 16.4L of nutrition product every week! In my own euro country, I can buy this stuff at about 17.50 euro a litre. So this would mean that I require roughly 290 euro's worth of nutrition every week. Which feels like a lot! Sure, I can try to buy this stuff in bulk overseas to get it more cheaper. But even if I could get it at half the price, it still feels very expensive.

Is my reasoning very wrong here or are other RDWC growers also adding roughly 20 ml of pretty expensive stuff for each Gallon in there system as well?

Thanks people!

Go with dry ferts. I use mega crop 2 part, there are also tons of other that are well proven like jacks 321. If you wanna cut the cost then cut the water.

 

[Aqua Man]

Also many to water changes to often in the beginning and to infrequently in the end.

Fill the res. Use tops to steer ph and ppm. Change the water one you add back the volume of the system. Can go weeks in the beginning and days in the end depending on the volume of the system and how much the plants are drinking

 

[king_of_nothing]

Wow guys,

Thanks for the quick answers (also on the original thread)! I didn't expect to get feedback so soon in the original thread. But much appreciated anyway.

So what I understood from Milson's response on the original thread, is that I have to get into the salt business :) to make this worth my while or at least get the nutrition cost further down and keep a weekly cycle of adding nutritions.

I'll take a look at dry fertilizers as well.

The salts are new to me. I appreciate any suggestions on introductory reading material on the matter of making your own fertilizer.

I think Mospeada already mentioned something about his salt mixtures in his journal thread (link here).

1. monoammonium phosphate for P and N
2. monopotassium phosphate for P
3. potassium sulphate for K
4. potasium silicate for K


And then you still need a micro nutrition solution. And you also have to factor in whatever the micro solution has as additional macro's supplements.

Then you also get the PH-stabilizers in the mix.

Maybe it is a more interesting statistic to know how much hydroponic growers are spending on nutrition per gallon of their system. I cannot find good resources on that except for what I have calculated for myself.

 

[Aqua Man]

Honestly I stay away from ammonium in hydro. Less than 5%.

There are many ways to mix your own depending if you do direct addition or concentrates. The ratios are important and the more sources you have the easier they are to reach your goals. But if not doing direct addition then it limits you to sources.

Honestly for the cost of dry ferts I would start there.

 

[Aqua Man]

A cheap simple way is find a good base nute. Buy some monopotassium phosphate as a PK boost and cal mag.

But something like jacks321 is just cheap and easy to use

 

[king_of_nothing]

Thanks I'll let this stuff sink in and get back on the matter later.

 

[king_of_nothing]

So I took a look at @BillFarthing's suggested link on open salts (link here) and focused specifically on GH flora series. Lets take "gro" as an example.

This bottle requires these three parts

Potassium Nitrate: 115,296.60 mg/l
Magnesium Nitrate: 49,408.67 mg/l
Mono Potassium Phosphate: 19,228.66 mg/l

Which I can get here, here and here respectively for €65.25/25kg, €38.26 / 25 kg and the price of the last one is not disclosed but I think it is half the price of potassium nitrate, so lets say €32.50/25kg.

That is already a lot of numbers so, I'll just leave you with the conclusion that I need about 40 euro cents or today 47 US pennies to make my own bottle of what is sold on my local Amazon site @ 17.50 a litre.

So if this pattern of money saving continuous for mimicking the other nutrition solution constitutes that I need, I think for my set up it would cost me about €10.50 a week for nutes which I initially taxed @ €480 a week 🤪😱.

I should be able to order these inorganic's as a private consumer without much hassle.

That's crazy money saving

Thanks you guys for helping me out!

 

[jemro86]

I just ran my first RWDWC grow using GH 3 part, and because of how efficient my system is, I couldnt even run above 400-500 PPM (500 scale) in late flowering, and I have high powered LM301H quantum boards too for the difference that makes. I literally ran there suggestions at about 25-35% on their feed chart. So keep that in mind, too. Compared to when I did 5 gallon DWC buckets and could get away with ~1000 PPM, I cant do that with the RWDWC.

Also, I know buying the GH nutrients by the gallon is A LOT cheaper then buying the little quart or 32 oz bottles...whatever the size is, lol. A gallon is usually only like twice as expensive as a liter bottle, but 4 times as much. Worth looking into, idk about your location though :(

Def look into dry nutes too - im kinda getting bored/tired with mixing all these nutes and additives and would like to maybe try something simpler eventually.

 

[smokedareefer]

We run a 4 site 13 gal current culture rdwc (small trees) and we are best to stay below 500 ppm on the 500 scale as well.

On day 28 of flower now and yesterday's reading before their feeding was at 390 so i bumped them up to 480.

My nutrient regiment consists of gh 3 part, cal mag (3-5 per gal) ph up or ph down.

 

[king_of_nothing]

I just ran my first RWDWC grow using GH 3 part, and because of how efficient my system is, I couldnt even run above 400-500 PPM (500 scale) in late flowering, and I have high powered LM301H quantum boards too for the difference that makes. I literally ran there suggestions at about 25-35% on their feed chart. So keep that in mind, too. Compared to when I did 5 gallon DWC buckets and could get away with ~1000 PPM, I cant do that with the RWDWC.

Also, I know buying the GH nutrients by the gallon is A LOT cheaper then buying the little quart or 32 oz bottles...whatever the size is, lol. A gallon is usually only like twice as expensive as a liter bottle, but 4 times as much. Worth looking into, idk about your location though :(

Def look into dry nutes too - im kinda getting bored/tired with mixing all these nutes and additives and would like to maybe try something simpler eventually.

Well it saves me like two orders of financial magnitudes if I am going to mix my own nutrition. And to be honest I like the DIY/bottom-up eningeering attitude to the problem. Buying by the gallon won't compete with that. It is interesting though that by your experience the feeding schedule of GH is too generous with its own product. But on the other hand perhaps it should not be that surprising: they sell this stuff for serious money. So a company provided luxurious feeding schedule factors on that all the more of course.

 

[king_of_nothing]

@jemro86 and @smokedareefer thanks for the hints at the 500 ppm threshold.