Two things I don't understand about growing RDWC

My transition from coco to RDWC has not been a smooth one there are many things I don't know about RDWC but the two things on my mind just now are.

1. I used Silicon in coco but I am led to believe when used in RDWC the plants will consume it and cause PH drops. Is this true, is there any way around it or should I just drop silicon.

2. When I get to say 4 weeks and want to add PK or a booster at 2 weeks how do I flood the full system at full strength PK or Booster. If I add it to the header feed tank it would take days if not weeks to be at full concentration in the system. If I slowly added it to the epicenter it would push the EC to high. I had decided to join the zero change out camp as I have a different system for veg so they would get a changeout on day one of 12/12. Is this one of the reasons many RDWC growers do changeouts at strategic times in the bloom cycle

fartoblue said:

If I add it to the header feed tank it would take days if not weeks to be at full concentration in the system

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explain. or a pic. adding nutes or anything for that matter to a rdwc takes only as long as it takes to cycle the water once.

#1 easy. dont use it.
#2 I dont understand the question.
#3 Have a look through the forum,plenty of fantastic threads and journals full of info.

Sorry I didn't explain question 2 very well (it was 12 40am).

In this scenario I am 4 weeks into flower, 300 litre RDWC 8 plant system with a 200 litre header feed tank nearly empty. My feed chart says at week 4 to add 10ml of PK per 10 litres and top up with base feed to 1.2 ec. The only way I could get that solution into my system at 4 weeks would be to drain and refill the system. If I put the PK solution into the header tank to drip feed it would never really be at full strength PK as they would only be drinking around 20 or so litres each day and the 20 litres coming from the header tank would be diluted with the 300 litres in the system.

In coco my first feed at 4 weeks would contain the full 10ml per 10 litres of PK and into the 5th week it could be reduced exactly to 5ml per 10 litres. It is the slow dilution from the header tank into the system. I don't understand how can I time the changed accurately from week to week.

Another thing is, in RDWC the nutrients are fed at a much lower ec so do I also half the quantities recommended for boosters and pk?

In rdwc,the water level stays the same through out the grow.You top up every day.

Yes you can flush and refill with added pk or you can add daily.Each day you add more to get the ratio you want.This can take afew days.

How big of pump do you have ?

With the way hes explaining his RDWC it sounds like it may be a water farm? Not a true RDWC so his water turnover rate isnt instant, takes a few days to cycle the entire system.

My RDWC is the same as Current Culture only diy 50 litre tubs. My question is at 4 weeks how do I get full pk dose/content into the full 300 litre system.

I can only think of

myke said:

In rdwc,the water level stays the same through out the grow.You top up every day.

Yes you can flush and refill with added pk or you can add daily.Each day you add more to get the ratio you want.This can take afew days.

How big of pump do you have ?

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My RDWC is the same as Current Culture only diy 50 litre tubs. My question is at 4 weeks how do I get full pk dose/content into the full 300 litre system.

I can only think of a full change out adding 300 litres of new pk enriched nutrients or a partial change out adding a strong solution of PK and water for example remove 40 litres from the system and add 40 litres of treble strength pk very slowly.

I Hear people here saying they do zero changeouts for the full grow but if 8 plants are only drinking 20 litres each day it would take 15 days before the system was at full strength pk. if feeding from the main header tank or adding daily.

My system

Top off each site and maybe the header tank with the strength solution you want in them? Then as it works into the system it will just mix in at the correct ratios.

Ya as said top each site. But I see no problem with adding 150 ml of pk to 30 litres of water and pour it in the Rez a little at a time. Let the pump recirculate it in. Next day add another 150 ml. Easy.

I’m not familiar with what current culture is?

@fartoblue

Yes, keep using the silica.
What silica product are you using?
A pre-mix (Armor-Si, Rhino (for)skin, Silica Blast, etc…), AgSil-16H, or Grow-Sil?

If you are using a pre-mix or AgSil-16H (same thing), then you will want to add this at the beginning when mixing your fertilizer, but before you add anything.
So, silica first, then pH down to bring the water back into range, then fertilizer, then pH adjust again if necessary.

Don’t add the silica after the fertilizer or the alkalinity will cause some of the elements in the fertilizer to fall out of solution.

If you are using Grow-Sil, then this is pretty pH neutral, so you should be able to add it any time.
But I don’t have any experience with it so I can’t give you anything other than what the brochure says which is meaningless.
I do have some Grow-Sil and I am planning on using it soon, so I can offer a proper opinion once I have used it for a bit.

As far as your second question, I don’t use PK or “booster” so I cannot help you with this.
Sorry.

As far as change outs,
I don’t run RDWC, I think the whole DWC system has too many problems (root rot, etc..), but I do run modular Dutch Buckets and I was changing out nutrients every week and this got to be tedious, so now I wait until their reservoirs are half empty and I top them off with half strength solution and this seems to be working.
My yield last time around was the same as it has been in previous grows so nothing changed in that department and the plants looked good, so no complaints from them.

All I did was cut the calcium nitrate back when they went into flower and supplement it with ammonium sulfate, so the EC would stay within range.

Hello Chris thanks for your advice on using silica. I am in the UK and tend to use whatever silica Is in the grow shop (whatever is cheapest). My thoughts were as the plants consume the silica the PH would drop as the silica disappears.

Myke Current Culture are a big Canadian RDWC manufacturer.

I've just done a little experiment and drilled a 1mm hole in a bucket and filled it with 5 litres of water it took half an hour to run through so my idea is to switch off the header feed tank and let my system run maybe 20 litres low then add PK to 20 litres of water until I have hit my desired amount of PK (haven't done the maths yet} or untill my 20 litres of pk/water hit my desired ec, which ever comes first. I will then drip it into the epicenter through the 1mm hole. Just a few short bits of timber suspended over the epicenter to support the bucket and two hours later all done....Well that is the plan. I may even use this method with a five litre bucket if I need to raise/lower ph or increase ec quickly.

Funny how different parts of the world will come up with solutions.
Thanks thought it was a new way of growing. Can’t beat a simple rdwc system. Cheap and easy. Good luck,sure looks like you’ll have some great plants.

Sounds to me like you bed to build a waterfall system with the new 5.3 gallon buckets on Amazon. Waterfall systems eliminates air pumps and stones, mixes the solution several times over per hour, and is very easy to clean if built right with bulk heads and unions.

fartoblue said:

Sorry I didn't explain question 2 very well (it was 12 40am).

In this scenario I am 4 weeks into flower, 300 litre RDWC 8 plant system with a 200 litre header feed tank nearly empty. My feed chart says at week 4 to add 10ml of PK per 10 litres and top up with base feed to 1.2 ec. The only way I could get that solution into my system at 4 weeks would be to drain and refill the system. If I put the PK solution into the header tank to drip feed it would never really be at full strength PK as they would only be drinking around 20 or so litres each day and the 20 litres coming from the header tank would be diluted with the 300 litres in the system.

In coco my first feed at 4 weeks would contain the full 10ml per 10 litres of PK and into the 5th week it could be reduced exactly to 5ml per 10 litres. It is the slow dilution from the header tank into the system. I don't understand how can I time the changed accurately from week to week.

Another thing is, in RDWC the nutrients are fed at a much lower ec so do I also half the quantities recommended for boosters and pk?

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