Sitting WC saltwater for a week — high alk, calcium, pH

[trapphd]

Hey all — I'm trying to bring my alk down (from around 11 back to 9.5, where it had been). In doing so, I've been testing the water I use for water changes: the real ocean water that Petco carries from Catalina. Normally, the parameters in my tank are: 8.1 pH, 420-440 calcium, and as mentioned, it had been around 9.5 dkH until it recently rose to 10.5-11. If you're unfamiliar, the water comes bagged in a box in 5 gallon quantities, so I've been using 2.5 gallons for each water change on my Fusion 20 Peninsula. I just tested the remaining 2.5 gallons in the box/bag for my water change tomorrow in order to estimate how much (incrementally) I might bring the alk down, assuming it would've been around ~9.5 (per my typical tank levels as I've used only this water and RODI to top off). It tested at 11.5 and 12, respectively (I tested twice). So, it is abnormally high for what I've come to expect. Then I tested pH (8.4) and calcium (490), which also came in higher than what has been typical.

Forgive the potentially ridiculous chemistry question, but is there a chance that, after being opened last week to empty 2.5 gallons into the tank, the remaining 2.5 in the bag rose in parameters due to some air exchange mechanism? Or is it just a weird batch? I'm trying to understand if this method will be viable in the future (if not, I'll just do 5 gallon WCs). Any insight or hypotheses would be much appreciated, thanks!

 

[lapin]

If some water evaporated then salinity would rise along with some other elements. This could happen before (when they were bagging it) and after you opened it at home. Ph might go either way once opened depending on Co2/ Oxygen exchange,
My $.02

 

[tinhorse]

Most likely it was that high when you purchased it. If you would like to lower your parameters just ensure you are not adding any 2 part and the calcium and alk will drop naturally over time as your reef uses it up. To drop it faster, get some ro/di water add appropriate amount of a salt that has lower alkalinity and pH generally (instant ocean possibly) and do a 2-5 gallon water change. If the tank is stable and looking good I would just leave the levels where they are as many successful reefs run with those numbers

 

[trapphd]

If some water evaporated then salinity would rise along with some other elements. This could happen before (when they were bagging it) and after you opened it at home. Ph might go either way once opened depending on Co2/ Oxygen exchange,
My $.02

Of course! I can't believe I overlooked evaporation, especially when it's been so hot this week. I just checked and it's 1.0275. That represents a significant departure from my normal level of 1.0245. I wonder if the parameters will approach "normal" if I dump in the remaining into my 2.5 gal bucket and then top off with RODI? Thanks for your helpful input.

Most likely it was that high when you purchased it. If you would like to lower your parameters just ensure you are not adding any 2 part and the calcium and alk will drop naturally over time as your reef uses it up. To drop it faster, get some ro/di water add appropriate amount of a salt that has lower alkalinity and pH generally (instant ocean possibly) and do a 2-5 gallon water change. If the tank is stable and looking good I would just leave the levels where they are as many successful reefs run with those numbers

Good idea. I had been dosing Reef Fusion 1&2, which seemed to work well for calcium but clearly led to higher alk than my system was consuming. So I've adjusted and the calcium has been stable throughout (with a smaller dose) and have not dosed the 2nd part for alk at all.

 

[trapphd]

Follow-up for anyone who may encounter this "issue" in the future: I dumped the remaining bagged water into my 2.5 gal bucket, and sure enough, it had evaporated by about 10 percent (only about 2.25 gal). I topped off with my usual RODI to raise it to 2.5 total and then tested after stirring it up well. The readings are much more aligned with reasonable parameters! 1.0245 salinity, 430 calcium, 10.5 dKH, 8.3 pH. Just have to be cognizant of the WC water not necessarily staying at equal volume when I save it for the next week.

 

[tinhorse]

Use an old 5 gallon salt bucket to store your water in. Air tight so no evaporation and great to pour out of.

 

[Randy Holmes-Farley]

Follow-up for anyone who may encounter this "issue" in the future: I dumped the remaining bagged water into my 2.5 gal bucket, and sure enough, it had evaporated by about 10 percent (only about 2.25 gal). I topped off with my usual RODI to raise it to 2.5 total and then tested after stirring it up well. The readings are much more aligned with reasonable parameters! 1.0245 salinity, 430 calcium, 10.5 dKH, 8.3 pH. Just have to be cognizant of the WC water not necessarily staying at equal volume when I save it for the next week.

Thanks for the update!