Top off res with nutrients or just water?

Hi, after mixing a fresh reservoir of nutes (in an aero system), the ppm was 1350. 24 hours later, it was just under 1000. Next day, it was under 800 â?? a pretty weak level for foot-plus plants. Iâ??m a complete newbie to hydro, so I was wondering: should I be replacing what they eat everyday (bringing the ppm level back to 1350 daily), or should I let the plants drain the drink down to [whatever it is after a week]?
I read on this forum one opinion that replacing what they eat is good. But logic is also telling me that since they consume different nutrients in different quantities, there would be no way to know what balance of nutrients to add back. For instance, if the plants dropped the reservoir ppms by 300ppm, and almost all of that was N, Mg and K, but almost no P,K, or Iron. If one were to add-back using the same bottled nute formula, then the depleted amounts of N, Mg and K would be replaced, while the [unused] P,K and Iron levels would be doubled â?? not a good idea.
On the other hand, if I leave the reservoir alone for a week, after a couple days when the ppms drop drastically, then foot-tall plants are getting a nutrient-strength right for clones.
My only solution to the quandry is to change the whole reservoir more frequently, like every 4 or 5 days instead of 7.
What do you all think about this? Or, what do people in the â??real worldâ?? actually/usually do?

P.S. The reservoir has a float valve and never gets low on water, so the observed ppms arenâ??t being affected by the water level dropping.

peace

Most growers suggest topping with just water.

Grow,

Interesting problem. I trully don't know the fix to it. Let's wait for input from me experienced people. BUMP!

I find that your answer will be very insightfull... as I'll probably see similar problems when I start my grow.

I don't have that kind of drop in my rez,. When I first strated some peeps don't empty but half there rez and fill back with water and nutes. I remember that if it drops that much I would use half nutes and water till rez change.

my vote would be to addback fresh water with half strength nutes until your reservoir change. If 1350 to start is strong enough, I would bring it back to at least 1200 after it dips down to below 1000. I have never heard of someone over-feeding with a constant ppm of 1350 though.

Is your float valve connected to a water source that refills your reservoir with plain water when it gets low ?

Is it possible that you can have more nutrient solution in your reservoir, so that you dont need a float valve triggering more and more plain water diluting your reservoir??

I wouldn't schedule a reservoir change every 4-5 days. That will get old really quickly and you will kick yourself if you later find out that it would have been better to change once a week to two weeks with a few different techniques.

Ask Zandor, he will shed some light over to you.

I think it's better to fill with pure water because nobody can tell how much NPK stays in the mix. If the ppm drops to much maybe you need to change nutes more often, that mean that the plants are sumotori. I don't have that much difference. For instance, 7th week of flo, starting EC at 2.6 now it's 2.14 after 3 days, water level has not changed a lot, so i let it go until sunday, EC will be at around 1.6, still good, there is something to eat anyway...
Fhydro

When you take your reading it's for just the full NPK nutrient mix. The plants will use some nutrients and deposit others. Your PPM reading is only accurate for the time you mixed it. Once you start feeding the plants it will go down or up depending on the cycle the plants are in. After you mix the nutrients (NPK) you let it sit for about 5-min so the buffers get a chance to work. Now you can balance the Ph and start feeding your plants. When they drink up nutrients and empty 1/2 of your res you can bring it back up to normal level with just Ph adjusted water.

Do a full nutrient change every 7-1o day's for the best results.

Today, 3 days after the reservoir change, the ppm is down to 460â?¦â?¦.. guess they ate a good amount so far (down from 1350ppm) so maybe they can do without any more nutes for a few days. Maybe that keeps them from overeating and accumulating too high levelsâ?¦. That is, maybe every res change is like a cycle: they eat most of the food, then donâ??t eat much for a few days, then eat heavy again (next res change)â?¦â?¦
Or maybeâ?¦â?¦.. I donâ??t have any idea wtf. The life of plants is complicated, too complicated for me to understand.
Guess Iâ??ll keep the res topped with plain water, change it every week, andâ?¦â??enjooooy the simplicityâ??.

I have always followed the concept of topping off with ph'd rowater only, but I read another opinion about this and for my current grow I am topping off with ph'd rowater w/3-part/or nutes only. No additives; So far they are growing tremendously, without problems...I like to experiment, so this works for me. It might be the method that you prefer, but if not...I have always had success by just topping up with ph'd rowater...goodluck.lw

Quote:

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Originally Posted by cnd411

Most growers suggest topping with just water.

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really?

I always thought the opposite.. especially since all books I have read say to change the resivor..

that being said..I always top off..
especially when the plants are late into veg and flowering.. they consume so much water and nutrient that I have never had a problem..

Although I hate to admit it, I like tormcookers thoughts about adding 1/2 strength.. and just build up...

I have always heard what Zandor said.. change resivoir every 7 days...

NEVER done it myself but....

i love you


either way, you should keep a close eye on your plants.. they will tell you what they need


i love you

my plants are drinking a lot and i use an aeroflo system as well...i top off w/ plain water following the golden principle of "underfert is better than overfert"....at least your plants wont die and you can observe them and add nutes if they show any deficiencies (mine never have)

Well, the problem is more simple i think. If the water level drops with the ppm level, putting plain water would drop the ppm level as much. So, except if there is nearly no water, you must consider the problem, but if the PH is good and only the ppm level drops ( and water a little also ), don't do nothing. Yes, one thing, change the nutes avery week. I add water only in case of PH problem ( low PH ). During one grow, i added normal mix of nutes to top off the rez ( summer, heat, evaporation ) and i had a serious over fert problem. I think that the ppm dropping means only that they eat the nutes.
Fhydro