Ebb Flood and drain - When and how to change water

I am going to be using an Ebb Flood and drain system and have been getting a lot of different opinions on when and how to change the water tank,



Some change every week



Some don't change at all and top it up



Some change every few weeks.





Changing once a week seems a bit OTT due to the expense of nutrients.



Personally i wanted to find a happy medium between all methods and try and top it up when need be, and change the water maybe every 2 weeks, but then how would i keep the nutrients correct? Would i just add water, or a watered down solution of nutrients?



All advice would be much appreciated, but as i stated i would really only like to totally renew the tank every 2 -3 weeks.

I run a ebb and flow table and here is what I do.

All the plants are in netpots with hydroton, no hydroton in the table, but the table is covered with panda plastic so light doesn't reach the water.
I flood the table 15mins on 45mins off, 24 times a day.

I never change the res just add back what was taken, same res from veg to flowering
I run Lucas Formula (Bloom+Micro) for the nutes.
Lucas says keep your PPM @947. So whatever the plant eats I add back using this calculator http://www.lucasformulacalculator.com/ .
I am week 7 of flowering right now and the plant has been drinking 1 gallon of water a day. So I add back water then I check the PPM and make sure its close to 947 as possible usually the PPMs stay around 850-950.

I on the other hand change every week or two at beginning and 3-4 days near the end. I'm a real newb and find it less confusing lol. Yes it does use more nutes but in my case they are relatively cheap with a gallon of A & B costing $35 and lasting 3-4 runs. I watch PH and when it starts to drop rapidly I change. I have never tried to add back but am sure if you know what your doing it works great. Also I thought Lucas formula recommends changing after you have added back the total amount of the res. I guess thats wrong, i must have misunderstood.

i used to top off but started to have ph swings and deficiencies shown by the plants. ever since then i have been changing weekly. ill never go back

Different things work for different people. After years and years of running F & D tables I now change my nutes every 7 - 10 days and like Myles I don't top off. I can if the solution level gets too low, but more often than not, it's not needed.

I run the Useless Formula using GH 3 part nutes.

i change my rez every 2 weeks and have been running the same system for 4 years now with no problem i top off with water when needed but thats it i use general hydro 3 part system plus floranector, florablend, koolbloom, diamonnector, floricious grow and bloom and have had great results

nothing grows in ur rez with the two week cycle and no sterilizing agent?

I have been lazy and seen my rez go 2 weeks with no problems. I never use any H2O2 or bleach or anything. I use GH 3 part, cal mag, ph down, florabloom, and florablend and that's it. Never had root rot, never had a nasty rez. Except that one time I used Flora Nectar. Start clean, stay clean. Keep your rez moving.

with all hydro i have used dwc/nft ebb i always top up i find plants can stay healthy for many months over 6 months
replacing the res is just extra work and a waste of food imo
although this is partly due in my case to having a very stable water supply that will always be 7.2 ph and .2 ec
and using one of the main brands of food (vitalink) or canna etc which is designed for hard water and has ph buffers chelates etc
which helps to keep the food (micro nutrients available at a much wider range of ph values
for this reason i also do not need to do any ph checks or alterations during the grow

if you have a less stable domestic water supply and were thinking of using more home made recipes as a food supply or one of the less known brands that does not contain ph buffers/stabilizers
then it might be best to change the res every 2 weeks or so since this type of system would fluctuate much more with ec and ph
you might need to keep a closer check on these variables to maintain healthy plants

peace

I do mine monthly top off every three days with h202 and nutes I have little algae at the month mark, but that's just because of the OP's circulation and my lifestyle. I believe the best is to do a biweekly.

I change out biweekly with topping of with ro+cal-mag during veg. Never had any problems and my temps stay at around 72 degrees . Roots are Nice a white