Calcium and alk increasing without dosing

[snk_anindya]

Hi all,
My tank is one year old. For the past two months, my ca and alk levels have been continuously increasing. I have not been dosing anything for ca and alk in the past two months. When I test a fresh batch of saltwater it has alk under 8.5. As of today, my alk is 14.4 and ca is 500. I have been doing water changes to control them. But within a week, they start increasing again.

Following are the details of my tank and my alk and ca for the past two months.

Alk history

Ca history

There seems to be some imbalance. Something seems to be adding both ca and alk to my water. But I'm not able to figure out what it is.

 

[snk_anindya]

Also, a bit of history about how I ran into this problem. My alk and ca levels used to be fine. They used to reduce gradually and I was using two part dosing to maintain them.

Around 4 months back, my nitrates and phosphates were messed up. I had huge algae issues of all kinds. Finally I ended up with lots of hair algae all over my rocks and also sand. At this point, nitrates were around 0.25 and phosphates were zero. So, in order to overcome the algae issue, I tried to rebalanced the nitrates and phosphates and get them to a higher level. I started to dose potassium nitrate and trisodium phosphate. Around two months ago, my nitrates were above 10 and phosphates around 0.4. All the algae disappeared. And I had stopped dosing NO3 and po4.

But at the same time, the alk and ca started to increase. And its been increasing for past two months. I don't know if dosing nitrate and phosphate caused some ionic imbalances.

 

[HuduVudu]

What are the parameters for your water change water?

 

[snk_anindya]

Freshly mixed saltwater has alk of 8.5. Not checked ca. And my tank salinity is at 1.024. It has oscillated between 1.023 - 1.026 in the last 2 months. But now it's been at 1.024.

 

[HuduVudu]

The alk can go up with CO2 but calcium is another story.

 

[Hallowhead]

Could be a long shot, but have you tested your RO water or water you're using to fill your ATO? Tap could be loaded with Calcium.

Have you noticed a die off of coralline algae?

 

[snk_anindya]

Could be a long shot, but have you tested your RO water or water you're using to fill your ATO? Tap could be loaded with Calcium.

Have you noticed a die off of coralline algae?

I've not tested my tap water. Will check today.

I have very less coralline. Can't make out of its dying.

 

[Randy Holmes-Farley Verified Community Expert]

Rock and sand can (will) slowly dissolve deeper inside where pH is lower, adding alk and calcium. Many long time reefers have to periodically add sand to maintain levels. Larry Jackson specifically mentioned doing this.

Solutions are to increase demand with users in the water, or do water changes with a lower alk mix, or very slowly and carefully lower tank alkalinity with a mineral acid such as sodium bisulfate.

 

[snk_anindya]

Rock and sand can (will) slowly dissolve deeper inside where pH is lower, adding alk and calcium. Many long time reefers have to periodically add sand to maintain levels. Larry Jackson specifically mentioned doing this.

Solutions are to increase demand with users in the water, or do water changes with a lower alk mix, or very slowly and carefully lower tank alkalinity with a mineral acid such as sodium bisulfate.

Hi..
If I try to lower alk by using acid buffer, what will be the effect on calcium? Will it lead to a situation of low alk and high ca?

 

[snk_anindya]

By the way, I just wanted to mention that I am using aquaforest Synthetic Rock and aquaforest sand. Any idea if this is prone to dissolving in water?

Also, I had added few large pieces of dead coral to the scape. Does this contribute to more alk and ca by dissolving?

 

[X-37B]

Sodim bisulfate will work but you need to go very slow as in small amounts at a time.
It will lower ph very fast if to much is added.

You need a ph meter and I would also run an airstone to help decrease levels of co2.

Unless you are comfortable and have the needed equipment water changes are your best bet.

Most do not recommend adding sodium bisulfate to an establised tank as it can go south fast if its not properly monitored.

 

[Randy Holmes-Farley Verified Community Expert]

Hi..
If I try to lower alk by using acid buffer, what will be the effect on calcium? Will it lead to a situation of low alk and high ca?

It will have no immediate effect on calcium. Lower alk will slightly reduce the daily demand for alk and calcium.

 

[Randy Holmes-Farley Verified Community Expert]

By the way, I just wanted to mention that I am using aquaforest Synthetic Rock and aquaforest sand. Any idea if this is prone to dissolving in water?

Also, I had added few large pieces of dead coral to the scape. Does this contribute to more alk and ca by dissolving?

Dissolution is generally so slow that the boost it makes are lost in the daily demand for alk and calcium by the tank. Any type of calcium carbonate sand and rock can very slowly dissolve. Silica sand will not.

If demand is naturally very low due to having few or no fast growing hard corals or other calcifying organisms, the boost to alk and calcium can be significant over time.

Other things raise alk too, such as falling nitrate or dosing nitrate.

 

[SigmaVX]

I have a similar post to this going as my Ca is on the rise for a year now with no dosing. A couple things worth noting are that my phosphate is around the same level and something I too am trying to control. Also I did clear up the sand bed a bit when there is algae because of the high nutrients and maybe that plays a role in the Ca? Anyone confirm/reject the role this could play?

 

[Randy Holmes-Farley Verified Community Expert]

I have a similar post to this going as my Ca is on the rise for a year now with no dosing. A couple things worth noting are that my phosphate is around the same level and something I too am trying to control. Also I did clear up the sand bed a bit when there is algae because of the high nutrients and maybe that plays a role in the Ca? Anyone confirm/reject the role this could play?

I replied to the other post with likely possibilities. Slow dissolution of sand can release some alk and calcium from it (but not one without the other).