Why does my calcium rise without dosing?

[ItalCanadaReefer]

Hi all, newb here. I only have a couple of small softy frags in the tank so my calcium needs are minimal. However, after testing with Salifert test kits for the first time a few weeks ago, I noticed that my calcium was high (above 500 ppm). Since then, I have done a couple of water changes and noticed that once I complete water changes, the calcium drops to right around 500 ppm. But, as the week goes on, calcium levels Increase above 500 ppm again. I am not particularly worried about the fact that my calcium is above 500 as I have read multiple posts by @Randy Holmes-Farley saying this in of itself is not problematic, but I am just wondering how this can happen without dosing. Can anyone help to explain how this is happening and why? Not sure if it is needed but my alkalinity is around 7.0-7.3 and magnesium above 1500 ppm. Thanks!

 

[ccurnick]

Most likely testing error, or your salt mix in your water change water is not fully dissolved.

 

[ItalCanadaReefer]

Most likely testing error, or your salt mix in your water change water is not fully dissolved.

I do not think it is testing error; this exact same thing has happening for several weeks now, where calcium decreases after a water change and increases until I perform another WC. The salt mix is indeed fully dissolved, at least seemingly so. I store my salt and mix it with three pumps and at the recommended water temperature to avoid precipitation.

 

[TrevorL]

Most of the time when you do water changes it replenishes nutrients into the tank. I’m not sure if different salt mixes have calcium in them or not but that could be a reason I’m not fully sure.

 

[ccurnick]

For how long? Some salt mixes take up to 24hrs to totally dissolve. There is a BRStv investigates about it

 

[jda]

If you have sand or rock where bacteria can live, the pH can get low inside of the sand or rock and calcium carbonate can dissolve. This buffering is common and most with even a low, steady demand do not notice.

It also could be a testing error, but if you are using a good kit like a Salifert or Red Sea, then probably not.

 

[ItalCanadaReefer]

For how long? Some salt mixes take up to 24hrs to totally dissolve. There is a BRStv investigates about it

I wait a minimum of 48-72 hours before performing a water change. I premix 30 gallons of water and perform roughly 10 gallon water changes weekly. I do not think my water is not well mixed.

 

[ItalCanadaReefer]

If you have sand or rock where bacteria can live, the pH can get low inside of the sand or rock and calcium carbonate can dissolve. This buffering is common and most with even a low, steady demand do not notice.

It also could be a testing error, but if you are using a good kit like a Salifert or Red Sea, then probably not.

I have sand and rock but to my knowledge this shouldn’t increase calcium. I am under the impression that calcium should only be decreasing as time passes, never should it increase without it being added to the system. Off that this seems to be the case for me though.

 

[jda]

You should read up on calcium carbonate buffering. I doubt that BRS has made a video on it, but it does just what I described and it is chemistry 101 for reef tanks. This can be happen even more if you have low pH, which happens with closed up homes in the wintertime, especially during cold spells.

The basics is that your alk gets low (and in turn your calcium). The pH swings more with less buffer. The lower pH dissolves calcium carbonate and carbonate (alk) and calcium release into the water to help buffer the pH again.

The pH in the rock and sand is usually lower than in the tank where bacteria and microfauna have more acidic waste which affects the local pH.

 

[btb72]

Are you replenishing your evaporation with fresh water? Otherwise when salinity goes up the calcium levels would too.

 

[ItalCanadaReefer]

You should read up on calcium carbonate buffering. I doubt that BRS has made a video on it, but it does just what I described and it is chemistry 101 for reef tanks. This can be happen even more if you have low pH, which happens with closed up homes in the wintertime, especially during cold spells.

The basics is that your alk gets low (and in turn your calcium). The pH swings more with less buffer. The lower pH dissolves calcium carbonate and carbonate (alk) and calcium release into the water to help buffer the pH again.

The pH in the rock and sand is usually lower than in the tank where bacteria and microfauna have more acidic waste which affects the local pH.

Ok thanks a lot for this! Much appreciated will read up on this. Thanks for pointing me in the right direction.

 

[ItalCanadaReefer]

Yes, luckily I’m a little better than that lol. Thanks!

Are you replenishing your evaporation with fresh water? Otherwise when salinity goes up the calcium levels would too.

 

[jda]

When you get a chance, read everything on Chemistry that Dr. Holmes-Farley has written. The only one that I tell people to skip are the ones on ORP, unless that stuff just really fascinates you.

Need to understand how phosphate binds to aragonite, the whole nitrogen cycle all the way to turning no3 into nitrogen gas (not just no2 into no3) and also the different types of phosphate/phosphorous/organic/inorganic and how most corals get their nitrogen from ammonia/ammonium and not from nitrate. Understand these and you will be well ahead of most on here.

Since we are possible talking about buffering, also smart to read up on how co2 in your home has a massive impact on tank pH. Air it out as much as you can.

 

[ItalCanadaReefer]

When you get a chance, read everything on Chemistry that Dr. Holmes-Farley has written. The only one that I tell people to skip are the ones on ORP, unless that stuff just really fascinates you.

Need to understand how phosphate binds to aragonite, the whole nitrogen cycle all the way to turning no3 into nitrogen gas (not just no2 into no3) and also the different types of phosphate/phosphorous/organic/inorganic and how most corals get their nitrogen from ammonia/ammonium and not from nitrate. Understand these and you will be well ahead of most on here.

Since we are possible talking about buffering, also smart to read up on how co2 in your home has a massive impact on tank pH. Air it out as much as you can.

Wow thanks so much for this. Knowing what to read is half the battle so this is very much appreciated. Awesome