What Should I Add To Tap Off Water?

[reeftankdude]

What should I add to tap off water to maintain a decent PH and other essentials? My PH is currently 7 using Instant Ocean salt and RO water. Thanks all

[Jaren45]

most people would use kalkwasser, but you have to be very careful not to spike your alk. if you're going to add anything try to do it slowly and start small

[burtbollinger]

i would not add anything to plain RODI top off water.  tankwise, I'd monitor alk., and make sure it was staying relatively stable from week to week around water changes.

[empresto]

The only time I add something to my top of water is when I'm specifically trying to solve a problem and don't have a free dosing pump. For example, my 40B is forever low on phosphates, so I typically test phosphate consumption prior to filling my ato reservoir and add brightwell neophos in sufficient quantity to meet demand (you need to know how long it takes for your ato to use up the reservoir for this to be useful).

Sorry, that was all probably clear as mud, but the key takeaway should be this: Unless you have a water parameter you have been testing and are intending to fix through dosing via the ato, you should not top off your tank with anything other than rodi water.

Also, as an aside, if you're core water chemistry (alk, ca, mg) is within appropriate range and your house isn't hermetically sealed, there should be no need to specifically adjust the ph of your tank.

[mcarroll]

On 1/21/2022 at 7:33 PM, reeftankdude said:

What should I add to tap off water to maintain a decent PH and other essentials? My PH is currently 7 using Instant Ocean salt and RO water. Thanks all

I'd check that pH measurement.  Whatever you get for pH after mixing a batch of Instant Ocean and RO water – 0.5 cups per gallon, right? – it should be "around" 8.0.   Anything significantly more or less than 8 (like 7) means that either your saltwater or your pH test is broken.

 

Pure RODI or even tap water might test at pH of 7.

 

 

[Swymer]

 I add a little tropic marin bio calcium to my ato reservoir to help compensate for the alk, calcium, and trace elements that are being used up within the system. Not sure if this is the correct way but it seems to be working and I've been doing it for years. Plus I learned awhile back that you aren't suppose to just add raw RO/DI water due to the fact that it can deplete trace elements from your system.       

 

And I agree with mcarroll; something is definitely amiss if your salt mix mixes up to a pH of 7. Most likely you need a new test kit.        

[Jaren45]

8 minutes ago, Swymer said:

 Plus I learned awhile back that you aren't suppose to just add raw RO/DI water due to the fact that it can deplete trace elements from your system.                 

where did you learn this?

[Swymer]

wetwebmedia.

[Swymer]

I also religiously buffer my RO/DI water several hours in advance before slowly adding the salt mix for water changes for the same reason stated above; to prevent loss of trace elements. I have absolutely no idea how true it is but it makes me feel better to do it this way.

[empresto]

14 hours ago, Swymer said:

Plus I learned awhile back that you aren't suppose to just add raw RO/DI water due to the fact that it can deplete trace elements from your system.

This is the strangest thing I've heard in a while. Maybe someone with a chemistry background can correct me if I'm wrong, but here are my thoughts on this:

1) where/how would the rodi water be locking up/depleting trace elements?  Since rodi is pure water, it is primed to take on elements, so should be able to hold in suspension all the elements needed for our tanks.  Rodi is typically known for dissolving things, not causing them to precipitate out of solution (Rodi will readily dissolve stainless steel plumbing, for example.)

2) Triton, ATI, and other ICP testing companies and trace elements suppliers would have this posted all over the place if it were the case.

3) Nearly all the best reef tanks I've ever seen use straight rodi for ato and for salt mixing, no 'buffering' or other changes, just straight from the reservoir.  My 4+yo tank has only ever been given pure rodi and it hasn't had any issues I haven't been able to trace to something tangible I did.

 

@Swymer If you can point me to the article on wet web media, I'd love to read it.  I'm unable to find anything like that on there with a cursory search.

[Swymer]

Maybe not trace elements but buffering elements.

 

I found this, not as an article but within the FAQs.

 

''Buffering RO/DI 2/14/06''

''I am currently running RO/DI water directly into my sump to top off one to two gallons per day as a result of evaporation. <<Yikes!  This is an example of "misuse"...adding raw unbuffered RO water to your system contributes to the rapid depletion of buffering elements as your system tries to make up for what the newly added water lacks>> I read that this is an acceptable practice, <<Mmm, no...not in my opinion...a recipe for trouble>> however, my pH has dropped into the 7.4 range and the alkalinity is at about 80-100 KH. <<And there is your proof my friend.  If you are going to run the RO/DI water directly to the tank then run it through a Kalkwasser reactor first...else I recommend you discontinue this practice and store/aerate/buffer the water in a separate container before adding to your system>>''

[Swymer]

Here's a link to the page. 

 

http://www.wetwebmedia.com/rotrtmt.htm

[empresto]

Ah, I see what they are doing here.  The first thing I'd point to is the year; this is 16 years old.  While they are not wrong in this respect, most of us are dosing to keep up with demand for buffering compounds (Alk, specifically).  If you have some way you are controlling the 3 major reef building elements (Alk, Ca, Mg), your method will also take care of any issues your ATO might 'cause' from adding RO/DI at a lower pH than the tank.  Now, if your method for maintaining those reef building elements was something more passive (e.g. some kind of Jaubert plenum or other deep sand bed type solution that was popular back then) it would be important to have your RO/DI come in with a pH matching the tank to not overwhelm such a method.

 

On the anecdotal side, I just tested my ATO reservoir pH and it is well below the 7.6 on the Red Sea pH card (I'd guess it is certainly less than 7, but I don't have a pH test kit for that low of a reading anymore).  However, the tank this reservoir dumps into does not budge from 8.2 pH unless my alk goes below 7dKh; doesn't matter when I measure the pH and the ATO runs sporadically all day adding ~1.5 qt/day to the 23-gal total system volume. The tank is automatically dosed with BRS Soda Ash and CaCl as the 2-part solution with occasional addition of Mg to match demand.

For salt mixing, I would point to the directions on most major salt brands that all have something along the lines of '...add the dry salt mix at the rate of 1/2 cup per 1 US gallon of fresh RO/DI water.' <- Tropic Marin Pro Reef Salt Mix Questions - Top FAQs - Bulk Reef Supply

 

Again, I'd love to hear the opinion of someone like Randy Holmes-Farley or another able chemist, but the above is my 2-cents for saving a lot of time worrying about messing around with 'fixing' good RO/DI water.