Question about topping dwc buckets

Is it okay for the ppms to fluctuate from 700 to 800 in the matter of 2 days on an auto flower?

When the ppms spiked I added more water to each auto to lower the ppms, because they aren't eating. They're just drinking water. So is it okay to lower the ppms with plain R.O water to get it back down to 700. They're drinking 2.5 gal of water a day in 20 gal. totes.

Also another question.. I have a a few other auto plants that I measured the ppms are at 600 exactly, and a day later they drank 2.5 gal. Of water and they're still at 600 ppms. So is it okay to add newts to the 2.5 gal. to keep ppms at 600.

Yes and yes, but you are doing a complete change every so often correct.

If they are drinking 2.5 a day then it would probably be a good thing to do complete change out every 5-7 days IMO.

Even in 15 gallons judges? Change them every week or so?

Sorry I thought you had said 20 gallons lol. Then IMO it should be like 5 days . I'm pretty new to all of this but it is my understanding that if you add back the total amount of the res it is time to dump it. I dont add back unless the res is running low and pump is in danger of pumping air, i run 30 gallons and change it out every 5-10 days depending on stage, I just find things are more stable doing that but I could be way wrong. Hopefully others pop in and school me as well lol.

A little fluctuation in PPM over time is normal. If your PPM is raising drastically, and water level si going down, then you are overfeeding. If it is drastic, I would do a water change and start with maybe half the PPM that you were using prior (So probably around 300-350 PPM). Then see what happens with PPM after a day. If it is not a drastic raise, then I would just add water back, which will bring that total PPM down a little.
On other hand, If PPM go down after a couple of days then you are probably underfeeding them. With that, I would add water back with nutrients to raise the total PPM by maybe 100 or original(At this time read your plant for any deficiency, and try to add a little extra of that...)
PPm staying exactly the same over a couple days, then your at your target. Here depending on the stage, I may or may not add nutrients when I add water back. I normally only add nutrients when they are in late veg to mid flower (Basically eating the most).

As for water changes. A lot of people hit on that. Change water completely every 5 - 14 days, depending on size and water use. A seedling doesn't need new water in 5 days, but a late flowering girl might. Adding water back between feedings is important. As someone said earlier, up to one full amount of original volume can be added back before full rez change is needed.

Perfect answer absolutely perfect thank you the exact answer I was looking for. Also Thank you for taking time out of your day to reply.

Blueberries said:

Perfect answer absolutely perfect thank you the exact answer I was looking for. Also Thank you for taking time out of your day to reply.

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But by adding back water only,,,your shooting yourself in the foot!

Try the old 33% rule of add back and I'll BET you'll be happier! Your plants will and you'll get bigger yields too!

Fill your res will 100% label directed (must be a QUALITY hydro nute) solution pH'ed to your set point!
Now put yer little ppm meter in a drawer and forget it!
As the res drops by plant use......make a 33% feed solution - pH it - top off your res!

Simple 33% solution = make one gallon of 100% feed and add 2 gallons of straight water - pH and use = 33% solution..

Keep track of how much you add back every top off.....When the amount of the top off will equal the amount the res holds or that you filled it with when you first filled it......DUMP and refill with 100% solution and repeat the process...

Even as the plant feeds and you refill the res......the ppms's should rise as the plant is putting back readable amounts of "waste" compounds.....It is not a rise in nutrient levels, but a rise in waste levels and that is what you need to get rid of at these "dump and fills"

Doc

NOTE: This is a form of "pushing" your plants.....Not hard but,,, it is "pushing" and you may get the little tips of the leaves indicating your close to "burning" but not actually "hurting" the plant!

I would NOT use any nutrient that has you constantly adjusting up the formula - Like H&G ! Pain in the ass!

HESI
G&H
Canna
etc. etc. Are great for this method.....

Adding back IMO is a crap shoot no matter what. But I guess with a DWC setup there is not much choice. (Never ran DWC) but by adding back are you not throwing the whole res out of balance, adding nutes or not.