Reservoir maintainence

I have a 3x3 ebb & flow running off of a 40 gallon res. I started with 10 plants, and now have 4 healthy ladies left. I am using AN nutes. I completely change my res every Sunday....fresh RO water and nutes. I am exactly one week into flowering. Here are my questions.....
1) I have a 40 gallon res, true, but would it hurt anything to only fill it with 20 gallons of water? If 40 is what should be run, why?
2) My PPM meter is shot, and I am broke to buy a new one, so would it be okay to just leave res alone for 7 days at a time (no topping off) between total changes?
3) If I am doing a total change every 7 days, and if topping off is recommended between changes, would plain water daily topping or every other day nutrients at 1/2 strength topping, be the better choice?

I hope this makes sense and that someone can help me, because I am not finding much. Thanks much everyone!

1. You can run a 20gal res as long as it still floods the plants adequately.
2. Top off with plain PH adjusted water each day until you change your res, otherwise it is likely the solution will become more concentrated as the plants drink it up, which could lead to nute burn.
3. Only use plain PH adjusted water.

A lot of people use this type of method:
1. Use 5 gallon res, have an extra 5 gallons of PH adjusted water.
2. Add water to the res as necessary until you use all the water.
3. Clean and refill.

With a 40 gallon res you definitely don't have to change it every week, even with a 20 gallon every two weeks should be fine.

platypusmann said:

I have a 3x3 ebb & flow running off of a 40 gallon res. I started with 10 plants, and now have 4 healthy ladies left. I am using AN nutes. I completely change my res every Sunday....fresh RO water and nutes. I am exactly one week into flowering. Here are my questions.....
1) I have a 40 gallon res, true, but would it hurt anything to only fill it with 20 gallons of water? If 40 is what should be run, why?
2) My PPM meter is shot, and I am broke to buy a new one, so would it be okay to just leave res alone for 7 days at a time (no topping off) between total changes?
3) If I am doing a total change every 7 days, and if topping off is recommended between changes, would plain water daily topping or every other day nutrients at 1/2 strength topping, be the better choice?

I hope this makes sense and that someone can help me, because I am not finding much. Thanks much everyone!

Click to expand...

You and I have a very close set-up, and the same nutes. I have a 45 gall. res, but I only fill it to 25-28. Entro is right you can go as low as your flood table will allow. I can leave my res alone for close to a week(I adjust ph whenever it needs it) I've somehow gotten my plants using a perfect ratio of nutes to water. So my res ppm stays pretty/very constant. Also..I've been doing a little test with mine. I haven't changed my res in 3 weeks. I added more water in week 1...nothing in week 2(since the ppms were constant) and I added more water and nutes in week 3. Hope this helps. You can always PM me Platy if you want to bounce ideas around with a AN bro.

Righteous...thanks and rep to you guys! I use RO water, and generally right out of the bottle my pH is 5.2 and with 10mL of AN pH Up I hit 5.7 and it easily stays there a week. When I was testing my ppm's (before I dropped meter in res and left it there 6 hours..LOL) they were staying constant for 4 or 5 days, and were not rising drastically. I just got in the habit of every Sunday after church when my daughter is off playing I break everything down & clean it, replace the res completely (with 40 gallons) and photograph & measure my plants. I only have 4 left...but they are gorgeous females and after only 8 days of 12/12 they are uber hairy (and one has grown 16" in 8 days)...so I am pretty sure they are happy. I have alot of experience with other plants, just not cannabis. Regardless...I felt 40 gallons was too much for 4 plants, so I am going to start running 20...it fills my table just fine. Also, it will greatly cut down on my nutrient costs, since I will continue to change it every week...it's just my routine and my time with my girls. I only see them about 5 minutes a day during the week, because I work for 10 1/2 of the 12 hours they get light each day. So, I really only see them on Sunday...I work M-Sat. So...anyway....blah blah blah. They are doing great and I think I will just keep doing things the way I am and just use less water and top it off with fresh each day.
Thanks again!!!

Sounds like a good plan!