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how often do i change my reservoir water in ebb and flow

  • by hydromax
  • Oct 12 2011 09:19 PM
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Posted 12 October 2011 - 09:19 PM

hello im running a 7 gallon 2 plant ebb and flow system and i would just like to know how often do i want to change my reservoir water and replace all the nutes and what not, anybody with any information on this topic help me out also a quick note i do not have a RO filter atm.
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  • Feesh

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Posted 12 October 2011 - 09:52 PM

7-10 days is usually suggested. I suppose you can go longer, but why would you want to? You risk the chance of algae and stuff like that.

You don't need an RO filter. Plenty of people do it with tap water and have zero issues.

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Posted 12 October 2011 - 10:55 PM

some say 2 weeks some 4 weeks helps control algae and fert salt build-up which will cause nute lock out

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Posted 13 October 2011 - 02:21 AM

Nice thanks guys. What about flushing with just straight tap water for a day? Anybody know about that?

  • Strain 23

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Posted 12 November 2011 - 07:12 AM

From personal experience it is best to change the resevoir once a week. This is for multiple reasons, I'll list a few.

The first being that you do not want to let your plants become deficient in any nutrients be they macro or micro. Plants use different nutrients at different rates not only from week to week but day to day. If you do not change the resevoir, and add only water, after a short while you will not have the proper ratios of nutrients to be absorbed and your plants may become deficient.

The second reason being that algae will colonize and grow at an exponential rate, and after a week you may possibly begin to see slime and gunk forming around your pumps and clinging to your walls. This is averted by using H2O2 or the DIY Clear Rez formula on a regular basis, but if you are against these two it's best to change the water and if possible give the resevoir a short cleaning every change.

The last and my personal favorite is when using organic nutrients or additives. They stink. Short and simple they can get pretty rancid with all the beneficial bacteria having a microscopic shindig in your resevoir.


Now if you want to let your water go a little longer be sure to keep an eye on it. It's best to change it every week, but whatever works for you, works for you. Just use common sense and don't be lazy with res changes lol. Happy Growing :smoke: ~23
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Posted 13 November 2011 - 10:03 AM

A week at the longest IMO
Flush with fresh and ph'd water for anywhere from one pump to a couple of days, maybe every 2 to 3 weeks when you change the water.

  • Strain 23

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Posted 13 November 2011 - 07:17 PM

A week at the longest IMO
Flush with fresh and ph'd water for anywhere from one pump to a couple of days, maybe every 2 to 3 weeks when you change the water.



A little bit of clearex also helps as well with the flush, maybe half strength maybe a little more. The clearex not only supplies the plants with carbs to assist in burning off the unused and stored nutrients in the roots and foliage, but also helps to break up gunk and clean your entire system. It is a great product. Another similar is Final Phase by AN. Both products will be a great help in the regular flushing and with your last week or two of final flushing. Happy Growing ~23

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Posted 05 December 2011 - 12:55 AM

Algae is harmless to plants. If you have a nutrient meter you should not have to change nutrients. Some people flush the last week of flowering but I do not.

If you will let your nutrients bring tap water down to 5.5-6.0 you will not have to add pH down which is what causes excess salt build up.

Yes plants may use nutrients at different levels but I highly doubt they will use so much of one that it becomes deficient. Commercial hydroponic facilities never empty and change their reservoirs because they maintain there ppm's at an appropriate level.

I have one reservoir for my plants in vegetation and one reservoir for my plants in flower. Neither reservoir ever gets changed. I simply top up with 1 gallon of water at 1/3 strength nutrients each day and the nutrients bring the pH down to the correct level.

If you are inexperienced and have the money to burn it will not hurt anything to change once per week but I have found that when a system get established unless you contract some sort of bacteria, it will self regulate.

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Posted 05 December 2011 - 03:37 PM

flushing 10 days before harvest will bulk plants and make them taste better

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Posted 18 July 2012 - 02:27 PM

Algae is harmless to plants. If you have a nutrient meter you should not have to change nutrients. Some people flush the last week of flowering but I do not.

If you will let your nutrients bring tap water down to 5.5-6.0 you will not have to add pH down which is what causes excess salt build up.

Yes plants may use nutrients at different levels but I highly doubt they will use so much of one that it becomes deficient. Commercial hydroponic facilities never empty and change their reservoirs because they maintain there ppm's at an appropriate level.

I have one reservoir for my plants in vegetation and one reservoir for my plants in flower. Neither reservoir ever gets changed. I simply top up with 1 gallon of water at 1/3 strength nutrients each day and the nutrients bring the pH down to the correct level.

If you are inexperienced and have the money to burn it will not hurt anything to change once per week but I have found that when a system get established unless you contract some sort of bacteria, it will self regulate.


i know this is old but i was looking around for this to see what other peeps think about their water. mine is a little 'rooty' right now if you know what i mean. before i continue i just want to say.... i couldnt agree more.

i find that it takes three weeks for my water to balance after i change it. i have to continually add ph down to get it below that 6.0 mark. and it more or less immediately goes back up to 6.2. i like 5.7-5.8 and i know that if i keep pouring in ph- i am eventually going to kill my plants. so i always give it a day or two to balance out before i go back and get pissed off that its back to 6.2.

then all of sudden, after a couple 10-20 gallon top offs... i sling in my nutes and the meter reads 5.7. the next day its still 5.7. a few days later and its 5.8. it is freakin magical and why would i want to go back to yellowing leaves. so i am ecstatic that someone else feels the same way.

instead of changing, i am gonna run down there and take a strainer to my water. i use 'root juice' type acids to eat away at the roots and although i do clean my rocks at every grow...there is always some left behind to dirty up my water. i never fool with cleaning it but this time around its starting to clog up my little circulation pump for my diy chiller. so i need to do something.

what do you do to keep it cleaned out?

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Posted 18 July 2012 - 03:08 PM

Ok through alot of trial and era ive learned alot about water. The only way your gonna get water that doesnt change ph is if you run in through a reverse osmosis filter. But they can be expensive so my solution was to check it twice a day and add ph down whenever it goes up then i change my water once a week and then scrub my whole res with betadine solution about 1 part betadine to 10 parts water. It gets all that grossness out of the res i also wash my pump and lines. Im also a nazi for being percise and super clean. But ive never had a disease root rot or anything. Its work but it works i wouldent do it any other way

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Posted 18 July 2012 - 04:37 PM

what we are saying is dont change your water at all and see how that goes. with new water... you have too many ph swings. with old water.... that doesnt happen. i havent had to put any ph down in, in three weeks. and i will not have to put any ph- in for as long as i do not change my water.

i came by this thread looking for someone that does what i do and i found him. i have run without changing or cleaning for up to nine months before. i just didnt want to be the only one. my plants have never had an issue and i have never used ro. it seems useless to dump 40% of each gallon you use. i have used filtered water and this time i am trying it without the filter and i really dont see a dif in how the plants act.

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Posted 18 July 2012 - 09:54 PM

I change my res only in the last 3 weeks of flower. That's when I add my dry koolbloom to finish up for 2 weeks. Then a week of water

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Posted 19 July 2012 - 02:44 AM

I change my res only in the last 3 weeks of flower. That's when I add my dry koolbloom to finish up for 2 weeks. Then a week of water


Question do you top off with plain water or nutes to keep your ppms up?

I change mine every 3 to 4 weeks. (mom and flower rooms). Also have 8 air stones

Edited by GreenMountain71, 19 July 2012 - 02:48 AM.


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Posted 19 July 2012 - 02:59 AM

Yes I top off with plain water. From what I understand water evaporates nutes don't. Either way when the girls are flowering they drink a lot of water.

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Posted 19 July 2012 - 04:19 PM

Do you use a ec or tds? Every top off my ppms drop example 840 ppms after i top off its 769. After 10 to 14 days its down to 500! I dont add nutes because im scared to have a lock out! Probably wont! But the way my luck is!
How long do you feed the 1st feeding for ,2nd,3rd? I feed 30mins,15,15. Ive seen some who feed for a 1h,1h,1h but those seem to be the ones who go back to dirt.

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Posted 19 July 2012 - 05:56 PM

for flower i change nutes every 2 weeks best way to prevent ph issues
for veg i might go 3 to 4 weeks but never more than 4 weeks
flood and drain veg table is fed every 4 hours for 5 minutes but lights are on 24hrs (flood and drain is a smaller version of ebb and flow)

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Posted 19 July 2012 - 08:20 PM

I have a constant read ph/ppm meter that's hooked up to a little float keeping the electrodes in the middle of the soup and not next to the walls or floor.

When in veg I only flood twice a day to promote root growth. U need to make them reach for the water. At a rate of fifteen minutes every 12 hours. If I feel them needing more ill add another flood. That's souly under my discretion.

Flower time comes around and I move my babies to there final resting place and flood her 4 times a day every 6 hours for fifteen minutes each. And that will be that.

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Posted 19 July 2012 - 09:06 PM

Do you use a ec or tds? Every top off my ppms drop example 840 ppms after i top off its 769. After 10 to 14 days its down to 500! I dont add nutes because im scared to have a lock out! Probably wont! But the way my luck is!
How long do you feed the 1st feeding for ,2nd,3rd? I feed 30mins,15,15. Ive seen some who feed for a 1h,1h,1h but those seem to be the ones who go back to dirt.


my ppms stay above 2k. they start at 800 when i stick them in my veg table. by the time they get switched to flower they are at 1500. about mid way through they are easily over 2k. and stay that way.

dont worry about lockout. i never have. and have never had an issue with it. i am not saying make a mix as strong as mine. just saying that its ok to give your girls some nutes.

my mix is 10ml gh bloom 5ml gh hard micro 1 ml gh floralicious. (veg and flower per gallon) and i use koolbloom as recommended throughout the flower.

I have a constant read ph/ppm meter that's hooked up to a little float keeping the electrodes in the middle of the soup and not next to the walls or floor.

When in veg I only flood twice a day to promote root growth. U need to make them reach for the water. At a rate of fifteen minutes every 12 hours. If I feel them needing more ill add another flood. That's souly under my discretion.

Flower time comes around and I move my babies to there final resting place and flood her 4 times a day every 6 hours for fifteen minutes each. And that will be that.


have you noticed a difference when you do not flush? i never have and have always thought i needed too. but i always seem to go for the weight.

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Posted 19 July 2012 - 09:56 PM

I have always flushed for about 3 days before harvest. Anything else is not needed. My flood trays don't really hold that much nutrients so clean water for 18 cycles seem to get all of it out. I also take out my rockwool cube and press it between my hands softly after I'm done and I set them in a dark room with no water at all. After 48 hours I harvest


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