PH and a Kalkwasser question

[hawkinsrgk]

This question really comes from another thread where Anthony Calfo answers a question explaining how using raw RO/DI water in ATOs over time is a bad idea. That's not exactly what was said because in no way do I want to misquote anybody, but that's what I got out of it.

So because of this last night I started doing some tests related to PH.

The PH in the tank at the high point is 8.36 when the ATO kicks on. The ATO is basically a float valve and switch connected directly from the RO/DI unit to the sump. This runs for 30 min a day through using a reefkeeper controller.

The RO/DI water (about 2 gallons a day) that goes into the tank has a PH of 5.5. Because of this after the ATO has finished the PH drops from 8.36 to 8.24. The PH at the lowest point is around 7.97.

I am thinking about adding a Kalk reactor because of this and run it between the RO/DI filter and the float switch but I have a couple of concerns.

Since I am still a newbe, my tank is around 9 months old and I have just started adding SPS frags which means at the moment I am not having to dose a lot of Calcium. My Calcium is pretty much staying at 420-440 by doing weekly water changes using a 50/50 mixture of Reef Crystals and Seachem Salinity salt. For ALK, I usually have to add 320ml of BRS 2 part a week and that keeps the ALK at 10Dkh.

So with all of that being said, I am afraid that by fixing the issue of water with a PH of 5.5 for top offs that it will cause a bigger issue with a very high value of Calcium over time.

Any thoughts or suggestions is appreciated
Thanks
Randy

 

[VegasRick]

Your pH is ok and well within acceptable range. There may be some validity to ro water contributing to the overall tendency of aquarium pH to slowly drift down. There are some arguments against it and I haven't given it enough thought or done enough research to have an opinion one way or the other. There are many many beautiful thriving aquariums with ph in that range, who don't use kw or buffer in their ro.

That being said at 9 months you should have some ca usage, even if its just coraline algae growth. There may be other factors as to why you are not using ca that I am not aware. With the additions of sps your ca usage should grow even more. You should be ok to use kw just monitor your ca alk levels and adjust your 2 part additions

 

[hawkinsrgk]

Hi VegasRick

Thank you for your answer. For Calcium I test the levels weekly after a water change and dose to 440 if I need to. Most of the time it is either 440 or 420.

 

[Stealth777]

RO/DI water, by nature is on the acidic side of the scale (usually 6.5 but in your case its a bit on the low side)

In short - to answer your concern, i offer the following solution:

Continue to use the ro/di water, but simply raise the pH from 5.5 to 8.0 with the simple addition of Baking Soda (sodium bicarbonate) to the ro/di water. The saturation point of baking soda in water is between 8.2 - 8.3 max so simply add enough to your ro/di water (then wait a few hours or so for it to stabilize - overnight preferable). You will now have pH adjusted water slightly below the levels of your main reef, without the pH drop you've been experiencing using straight non buffered ro/di water for your topoff.

Many reef enthusiasts choose to pre buffer their RO/DI water for TWO reasons.

• to get the topoff water to match tank pH parameters
• to get the topoff water to match tank alkalinity/carbonate hardness (KH) parameters (usually 8-11 dKH for reefs)

With the addition of carbonate hardness builders to your topoff water, you can reduce/eliminate the need to dose alkalinity to your main aquarium on a weekly basis, as its slowly being added to the reef via your ato system.

Personally, to keep things stable, I raise the pH of my RO/DI water from 6.5 to 8.0 with baking soda, and on the reef , i add either the alkalinity portion of the 2 part alone, or add superbuffer dKH as needed to maintain my alkalinity/dKH in the appropriate range.

Your calcium parameters are perfectly normal and will maintain that level until your SPS begins to grow and absorb the calcium creating a supply/demand imbalance. To be quite honest, if you are performing routine water changes every week (10%) or every 2 weeks (20%), your levels of calcium should always be within the 380 - 420 range absent of much coral to absorb it. Many reefkeepers have the issue of low calcium, even when they are dosing it daily/weekly - and the "fix" is usually due to low magnesium. So simply test for magnesium.

Also, I found this awesome article (very easy read) to solve ANY calcium/alkalinity imbalances you may have now or in the future.

Bookmark it:

http://www.advancedaquarist.com/issues/nov2002/chem.htm

All the best!

 

[hawkinsrgk]

Thank you Stealth for your help

 

[VegasRick]

It sounded to me like your top off water comes directly from your RO unit. If thats the case it would make it hard to add anything without either a holding tank for the ro or a kw stirrer.
Also you should get int the habit of adding your ca alk additives more frequently than once a week. Daily or constantly is best. A weeks time can generally be too much of a swing in parameters especially with sps. Stability Promotes Success

 

[Stealth777]

Yes VegasRick - I wasnt sure if he was running straight RO/DI water directly to his reef or from a holding tank via an aqua lifter pump triggered by the float switch. He wasnt specific, but either way, I think he's off to a good understanding that there's a few different methods in keeping pH and alk/KH stable. I'd like to hear back from him on which method he chose to use, and how its working. This website is great for idea exchange & advice.

 

[hawkinsrgk]

Sorry guys that I wasn't specific

The topoff water goes directly to the sump from the RO/DI. I am currently using this
Level-Loc auto top off unit for RO systems - English

and was thinking about adding Aquamedic Kalkwasser Stirrer / Reactor 1000 - English
after the RO/DI and before the auto top off.

I currently do not have a holding tank

 

[hawkinsrgk]

Since I'm currently using BRS 2 part, I knew I would soon have to start dosing ALK more than one day a week. Maybe three.

Im trying to determine how much of an issue 5.5 PH topoff water is and also reduce the PH swing of 7.9 to 8.36 or if Im making something out of nothing.

 

[VegasRick]

IMO its nothing to be concerned about. adding ca alk via top off or via 2 part all ends up working out the same. Only pure water evaporates and thats what you are adding back. The important thing is to keep the levles as stable as possible