How often do you change water?

The 1st time I used hydro I changed the water every week. Plants didn’t do well. I have read where some growers never change the water. So that’s what I am trying.
Plant is just starting to flower, PH is right around 6. So I’m looking for the experts opinion, change the water or leave it be?
This is what my plant looks like today.


I drain and change water half way thru veg and then a few weeks into 12/12.
Also any time there are big ph swings or root issues. These usually happen with new system I have to learn. So for my current grow just the 2 times stated.


I have been on a 12/12 for a couple weeks now. Thinking next time it gets low (uses about 4 gallons ever 2 days. Tank holds 16 gallons).

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I wouldn’t do that.

You can easily get away with it in VEG.

Back when I grew in DWC I never changed the res in veg but once that plant starts flowering it’s needs change drastically.

It will start eating more of certain nutrients and less of others and if you never change your reservoir you might get a build up of nitrogen in your nutrient solution in late flower and your plant hardly needs any nitrogen at that point.

Im sure there’s another explanation other than weekly reservoir changes as to why your plants struggled previously.


Looks like I’ll change the water today then.



I don’t grow in DWC anymore but I spent several years doing it.

It’s super important to change often in flower. That way you are the “scientist in control of your experiment”. If you just let it go all kinds of bad stuff can happen.

Some things that might have contributed to a bad grow previously could have been too high of water temps or not enough oxygen (I liked my water too look like it was boiling there was so much air in there), both those two go hand in hand.

Not having good ventilation and air flow is another potential problem. Many plants can still look good in the veg state with even bad ventilation, but once they start flowering then it will definitely show if you don’t have good air flow.

Anyways :v:


Water changed!!


Changing weekly is good. You need to get the algae under control. Keep the water on the roots, keep everything above the roots of plant dry.

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I read that a recommendation is a every 10 to 14 days but it always depends as well on your set up and maintenance but not more than 14 days

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I’m one those in the camp of if the girl looks good, her roots look good, just keep adding water. Usually I can go that way till final flush, but if Ph issues present, I flush rather than chase them. I tend to keep my feedings light to start and just cut nitrogen food early from my feedings.

I do a complete water change every 10-14 days in veg and change water in flower every 7 days in flower. My nutrient schedule changes every week or two in order to lower n and raise p,k. The water change also helps maintaining pH


I’m not sure if that’s algae , but a dirty environment will create unstable results , and if your using tap water make sure get rid of the clorox or whatever they use in the water, good luck

We have well water. Do God knows what’s in it. But plant seems happy.

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That’s why your having problems cuz you don’t even know what exactly is going into your plant , dont have a control environment anything can happen , that’s why you can’t control your ph , plain and simple you don’t understand why the fluctuations , I’ll give the answer you have living organisms in your water interacting with the proteins and mineral all the nutrients you put in , a quick chemistry example, yeast eats sugar , and as a byproduct creates co2 and alcohol, so I other words this is the reactions of bacteria interacting or eating sugar , now if you have Algie or living water ( meaning living bacteria) they are going to eat the proteins that you put in your Rez and as a byproduct they are going to generate other chemicals and that where the fluctuation comes from , bacteria is eating your nutes and pooping in your water and it’s not the bacteria that the plant need , I hope it helps , but that my point of view, clean that sht up

You can always get your water put it in a container put a cap of Clorox and put some air stones in there this will kill most bacteria from the water so you can have a better and more control water , you will need to let the water sit of 24 open container or put an airstone and let it go for 10 hours this will evaporate the Clorox , if you have a tds it’s really recomended to check before and after your tds to verify the tds - or reverse osmosis water , you need to kill the critters in your water before you mix it with rich nutrients , they are always long explanations and no body it’s going to give you the secrets cuz it takes time and effort , dedication , to understand, I would advise to read as much as possible in the future

Clorox… NO

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Remove Chlorine by Evaporation

The simplest way to remove chlorine is to simply let it evaporate from the water. Chlorine is a gas at room temperature, and in water it’s a “volatile solute” meaning its molecules are diffused in the water, and it will escape into the air over time. The amount of time needed varies with air and water temperature. Heating or boiling the water will speed the process. Another factor is the amount of surface area for the volume of water; a wide-mouth container will allow the chlorine to dissipate more quickly because it exposes more of the water’s surface to the air. This method will only remove chlorine, though, and many modern water treatment systems use chloramines. You cannot rely on evaporation to remove chloramines, so if you are changing a fish bowl, check with your water department to see if they use chloramines. If they do, you will need to use a different method to ensure safe water for your fish.

Yeah it it’s a lil more complicated than that but , so I guess I won’t since you have to know the science behind it , an I think I was being unclear , that’s to prepare the water for the next feeding, so it would have a more reliable source of water , and the Clorox would Evaporate by then . But there’s to much involve , probably would end up incorrect and burn the plant

I’m willing to bet any ph issues are from water temp causing root issues. Or an improper ph to start.


PH is right about 6 ( after using a bit of PH down). I haven’t really had any PH issues.