Marine Salt lower pH levels?

fearkitten

Reefing newb
I'm running a 30 Gallon reef tank (been up and running for about 3.5 months now) and keep encountering pH levels that are lower than recommended/normal and I fear what long term effects this will have on my fish/corals. All other parameters in my tank have been testing at normal levels but my pH runs relatively at about 7.4 to 7.5 on any given day. Everything in my tank looks healthy and happy at least, but I obviously want to do my best to provide the best quality water chemistry I can for my stock in order for it to thrive well in the long run.

After performing hours of online research I tested a couple theories and still have no real answers.

First I took into account that gas exchange may have a negative effect on maintaining my pH levels so I measured the pH of my tank water (7.5 as usual) and removed a glass full and aerated it with an airstone for an hour, then remeasured the pH of the water in the glass and there was no change. This was not really all that surprising to me though as I have adequate water movement throughout the tank (377 GPH) and one of my power-heads is specifically positioned upward to break the water tension and remove the chance of poor gas exchange in my water (also no lid for better oxygen flow).

Second I read in multiple places that using liquid Amquel can lower pH quite drastically in certain water conditions. I usually was using it to treat my tap water before water changes so I thought perhaps this was the culprit. I measured the pH of my tap water right out of the sink and it read at 8.7 pH.
Then after adding proper amounts of marine salt and Amquel to a 5 gallon bucket of tap water, I remeasured and it dropped down to 7.5 as expected. So for a moment I was convinced it was the Amquel. I dumped that bucket of water and made a new batch, this time I treated the water with Prime first - which, when added on its own into the freshwater had no effect on my tap's pH levels as they still read at about 8.7 but as soon as I mixed in my marine salt it dropped back down to 7.5!

Is it possible that the marine salt is having this effect? And if so why/how and what can be done about it? Or am I just an incredibly dumb newbie who is missing something really obvious? Any clues as to why this is happening would be very much appreciated! And apologies in advanced if this is a dumb question...
 
Hello and Welcome! There are no dumb questions!

But what is your calcium and alkalinity levels at. Those plus pH are intimately related and when one is off, it effects the other two.

But while we are on the topic of water chemistry, you should not be using tap water, unless you have a TDS meter and it reads less than 10 or 15 ppm. Tap water is full of nasty things that can kill your corals and inverts and feeding ugly algae. Using a decholorinator like Prime or Amquel does nothing to remove these things from the water column.

You should be using distilled or RO/DI water
 
Hello again, thanks for the kind welcome and reply...

Alkalinity: 10 dKH
Calcium: 420 mg/L

From past readings I believe these parameters are right/reasonable for my tank, correct?

Thanks for the suggestion - I will definitely take your advice on the tap water as I don't wish to add anything that could possibly harm my tank in anyway.
 
Do you keep your windows closed? Do you have air movement through your house? Do you have a lot of people living in your house, or around the tank all day long?
 
No, my windows and doors are open a majority of the day, so we have a constant breeze of fresh air and its only my husband and myself who live here - and in addition we have a lot of house plants so I feel like excess CO2 in my house would not necessarily be a contributor to the low pH.
 
Oh and just to keep this thread updated, someone on another board mentioned that perhaps the brand of pH meter I am using is not giving accurate readings because it is not properly designed to be used with saltwater. It is specifically made for gardening, which may explain why it reads our freshwater accurately at 8.5-8.7 but drops immediately to 7.5 range when marine salt has been added. Stores are closed now but I will purchase a new test kit or meter at the LFS tomorrow and go from there. Thanks again everyone! ^_^
 
So you are using an electronic pH meter? Definitely get a test kit made for saltwater aquariums. Get the droplet kind, not the sticks that you dip in the water.
 
What does the time your light have been on matter or people by the tank.

Answer both please.

I have tested my water in the morning when the lights have been off all night and at night after they have been on for 5+ hours.
 
When the lights have been off for a long time the pH drops because there is no photosynthesis going on in the tank. (the biproducts of photosynthesis raise the pH, this is why people run the lights on their fuge opposite of the main tank).

If you have a well insulated house or a house with lots of people, the air in house has an lower oxygen content and the pH of the water is lower because of that.
 
Yeah yeah ok I get it. I have been running my fuge light at the same time so I will just move the plug down on the digital timer. It is one of those when the 2 are on the other 2 are off but.......

That would mean the fuge light would be on for like 18 hours.
 
Phastroh, I believe you are supposed to measure your pH at relatively the same time during the day - ideally a few hours after your lights have been on. This is due to the fact that pH levels tend to drop during the night. This is because during the day, photosynthesis helps to consume/eliminate excess CO2 but at night this is obviously not the case and higher CO2 levels can cause a drop in pH. And the theory of people being around the tank is also relative to any excess CO2 (from you or anyone in your home breathing haha) lowering the pH.


EDIT: Oops, I guess your question was already answered while I was busy typing! >u<
 
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It was indeed the pH meter that was throwing me off. I purchased a droplet test kit today and my water is now reading at a healthier 8.1 instead of 7.5. So, lesson learned here - gardening pH or any pH meters not intended specifically for saltwater use will not produce accurate results for saltwater pH. Thanks again for your help everyone!
 
sure thing!

but this raises another question in my mind, do you have all the other test kits you need for saltwater like ammonia, nitrites, nitrates, alkalinity and calcium?
 
Yeah, the pH meter was the only questionable non aquarium specific form of testing I own. Everything else (ammonia, nitrate, etc.) I have droplet test kits specifically for saltwater. :)
 
Yep, exactly that... If you have a lot of people around your tank, and measure the pH, you may see a drop because all those people have been exhaling CO2, which forms carbonic acid when it mixes with water. The carbonic acid drops the pH.
 
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