Changing your nutrient reservoir? How often? Is it necessary? My answer might surprise you. I have a video that explains my take on topping off your reservoir vs changing it out.
Keep Changing Your Nutrient Reservoir
Your Nute Company Needs The $$$
Conventional wisdom tells us to change out the reservoir every week or two. And this bit of knowledge comes from the nutrient companies. It’s great for them because you buy more nutrients that way.
Do you like watching your hard earned money going down the drain? Unless you have something growing in your res there is no reason to do this.
I am not saying there is no need for hydroponic reservoir maintenance. If you use a lot of additives they may create gunk that needs to be cleaned out. If you are having root issues or lock outs you definitely need to sterilize everything and start over.
But if you are running hydroponics systems it is usually best to skip a lot of expensive additives especially if they are heavy on organics. If you are running DWC or a drip system they can often cause more problems than they solve.
I know many growers in DWC that never dump their nutrients. They simply top up and add H2O2 or pool shock to keep things sterile.
How Often Should You Add Nutrients To Hydroponics?
Only as often as is necessary! I will assume your system is somewhat dialed in and you know what nutrient levels to run. I also will assume you at least own a TDS meter Ph pen. Otherwise you will never know what to add when topping off your hydroponic reservoir.
Get A 24/7 Nutrient Monitor
Beats the hell out of always checking things with pens and you will know at a glance what is going on in you reservoir. I bought one thinking it was a luxury item for the lazy grower. I consider it a necessity if you want to grow quality weed.
You probably heard that plants use different nutrients at different times and in different amounts. They say if you dont change your nutrients regularly you could experience deficiencies. It is true what plants eat changes depending on their growth cycle. But since we are going to top up your res regularly there will always be a supply of fresh nutes being added. So dont buy into that argument.
How To Top Up Your Reservoir
You will need to figure out how much water your reservoir holds. You will need to grab a gallon milk jug or similar. Dont go by what the manufacturer says. Also a 5 gallon bucket holds less than 5 gallons unless filled to the brim! I have one of those 27 gallon black totes with the yellow top many people use. It is almost full with 20 gallons!
This is important because it will help you to mix your nutes correctly. If you add enough for 27 gallons and you only actually hold 20 your mixture will be too strong. There also wont be enough room to dilute it. Dont ask how I know this.
Calibrate Your Nutes
I like to grab a gallon bucket and mix a gallons worth of nutes and check the TDS and pH. Find your sweet spot. Keep track of how many ml you use of each ingredient. I RECOMMEND WRITING THIS DOWN SOMEWHERE FOR FUTURE REFERENCE. Most recommendations on your bottles are way to hot. Again they want you to use more. They dont really care about your crop they just want your money!
I use a piece of PVC pipe as a gauge. I work in units of 5 gallons although you could use a different unit. Every 5 gallons added to the res gets marked with a line. So I know for example my reservoir is filled with 20 gallons and if I know what a gallon of nutes is I know exactly how much to add to make 20. Make sense? Write down your readings.
When I go to my reservoir and check it I know exactly how much my plants have drunk. I add back enough water to bring my reservoir back. Say the level on my pipe is 15 gallons. I know I need to add 5 gallons of water to get back to the 20 original gallons.
BUT WAIT! Now you need to read the new reservoir PPM and pH. IF YOU SUBTRACT THIS FROM YOUR FIRST READING YOU WILL KNOW HOW MUCH YOUR PLANTS ATE. So if I was running at 1000 PPM and now its 800 they ate 200 PPMs.
More importantly I know how much nutrient I have to add to bring it back to the same level. It is 200 PPMs.
That’s why you measured a gallon of nutrient mix a while back. Now you can mix a small batch and add back 200 PPM. There is no guessing and no over or under dosing nutrients for your reservoir.
How big should my hydroponic reservoir be?
Bigger is better! You want enough water for your plants but you also need to watch your water temperature in the reservoir. Also if the nutrient reservoir is small you will have to top up much more often. A larger nutrientres is more stable and less work to maintain.
Size will depend on the size of your grow and the system you use. Obviously you need a larger res for DWC or flood and drain than to run a drip system. I would say 20 gallons would be OK for a small grow like 1 light or less. But again more is usually better. Remember too that you wont be dumping your nutes every week or two!
Good luck and happy growing!