No DWC reservoir changes?

[Simplicio]

I've been noticing that plants seem to get stressed, and won't eat or drink much the day of a complete reservoir change. This is almost certainly slowing growth. I've been reading some things about how some commercial growers are not doing reservoir changes, so I googled this idea, and discovered that some home growers are also doing no res changes.

The accepted wisdom is to do them every 7-10 days. If 1 day of growth is lost for each res change (a questionable assumption), and the res is changed every week for 12 weeks, then a total of 12 days growth could be lost. Certainly, this is the worst case assumption, but it's possible that harvest will happen quicker without res changes.

I'm going to try a compromise method of replacing exactly 2 gallons of reservoir solution every day with fresh solution. The usable Res volume is 24 gal, so there will be a complete turnover every 12 days. That's not the same as a complete changeout, but should come close.

If this works, it will eliminate those dreaded res changes, and instead spread them (and the work) out over time. Along with reducing stress on the plants.

Has anyone else tried no or partial res changes?

 

[Sage]

I just finished a grow in a waterfarm type system,, it was a DP Automazar which came down on day 96, didn't change the reservoir once, just topped up when needed. I used RO water, Canna Calmag Agent, GH Flora Nova Bloom, Hydroguard and Cannazyme. Had zero issues, except the plant got so huge it was pushing against the light :smoking:

Go for it, if you do run into problems you can always change it out, but I'm pretty sure you won't though. Saves a ton of water too.

 

[Simplicio]

I just finished a grow in a waterfarm type system,, it was a DP Automazar which came down on day 96, didn't change the reservoir once, just topped up when needed. I used RO water, Canna Calmag Agent, GH Flora Nova Bloom, Hydroguard and Cannazyme. Had zero issues, except the plant got so huge it was pushing against the light :smoking:

Go for it, if you do run into problems you can always change it out, but I'm pretty sure you won't though. Saves a ton of water too.

Thanks for the reply.
I check my tank 3 times a day.
So far I've removed 2 gal, and replaced it with fresh nutes today.
But your experience makes me wonder whether I can reduce that to changing out 0-1 gallons per day.

 

[Mike20132]

It comes down to concerns of unused nutrients building up too high concentrations. I ran into problems on my first (and most previous) grow for what I believe to be that exact reason.

When I discovered and addressed the problem, I did so by completely draining the res, and refilling with fresh nutrient solution and a dose of VooDoo to rebuild the bacteria colony. Later on, I would even flush through a gallon or so of plain DI water just to make sure I got it clean. While this seemed to work, it used a LOT of water. I wound up buying a distiller because I got sick of hauling the stuff home from the shops. In retrospect, I can't help but wonder if that contributed to the 100+ days before harvest.

I think this time around, I'll just drain between 1/4 and 1/2, preserving the bacteria colony and lessening the "shock" of the chemistry change as much as possible.

It's not mandatory in every grow, but IMO it's probably not a bad idea if it helps prevent a lockout problem before it occurs.

 

[BRICH999]

I did one majority water change and have the last couple grows. Between veg and flower I let water get low and drain out most of what's left. Best guess 6gal left out of usually 25gal. Mostly done it out of being lazy but haven't noticed drastic impact.

 

[MedGrower]

Reservoir change does not stress the plant nor it will stall your plant, provided you do it right; Not changing the pH, EC or temperature of the solution too much at one time. I do change my reservoir once a week just to ensure there is optimal balance of nutrients available. Still it is a good idea to leave a little bit of the old solution to the bottom to allow remaining beneficial bacteria in the solution to carry on to the new patch.

I see the desire to work without the reservoir change, and for small and young plants you can get away with it a lot better, but in the end with large plants sucking up multiple litres per day per plant, there is a potential of ending up in trouble with buildups that lead to nutrient lockouts. Then again.. I still see the desire to do so.. it may even turn out to be a fine art to grow that way?

 

[Mike20132]

Reservoir change does not stress the plant nor it will stall your plant, provided you do it right; Not changing the pH, EC or temperature of the solution too much at one time. I do change my reservoir once a week just to ensure there is optimal balance of nutrients available. Still it is a good idea to leave a little bit of the old solution to the bottom to allow remaining beneficial bacteria in the solution to carry on to the new patch.

I see the desire to work without the reservoir change, and for small and young plants you can get away with it a lot better, but in the end with large plants sucking up multiple litres per day per plant, there is a potential of ending up in trouble with buildups that lead to nutrient lockouts. Then again.. I still see the desire to do so.. it may even turn out to be a fine art to grow that way?

100% could not agree more. The faster the plant takes up solution, the more likely you are going to start seeing a buildup of unused nutrients. And it is astounding just how thirsty they get when they are really into flower.

For about 3/4 of the grow, the solution uptake is slow enough that you can work your way towards "getting it right" with the nutes. Once she's into full-on flower production.... well you just have to hope you already got it right. Especially with smaller tank sizes. In that case, weekly flushes make a hell of a lot more sense given that it is very difficult to see a problem happening before it's negatively impacting the grow.

I think with the current grow I will go with a flush after the first two weeks, then two weeks after that flush weekly until harvest. It's a pain in the ass, but if you don't shock it with insane chemistry changes by waiting too long, it should, as you said, be just fine. Leaving at least 1/4 of the original solution at each flush is probably the lowest i'll go. Will still add the VooDoo anyway just to make sure there are microbes-a-plenty.