Aragocrete and Alk

[GeoSquid]

I made some aragocrete about 7 years ago with aragonite sand, oyster shells, Portland cement and rock salt. I cured outside for months in a tub with a pump. I've had it in my tank for all of those 7 years. I used to have to add alk all the time years ago, but for at least the last 2-3 years my alk is ~14 and it wont drop. I haven't added any alk supplements in years now. I have all soft coral, but can't grow any LPS or SPS. They die within a month or two. Has anyone had aragocrete in use this long? I am thinking this is where my high alk is coming from. I made a lot of it for my 189 gal.

 

[Rocks reef]

You alk is quite high, yes. Which is why most corals are doing well in your system, however, there could be other factors involved as well. The aragocrete is more than likely leaching into your system.

@Randy Holmes-Farley
@ReefSquad

 

[Fish Fan]

I don't know, following to see what the experts tagged in above have to say, but I would think after 7 years submerged it would have given up the ghost by now.

What are you using to measure your Alk?

 

[Randy Holmes-Farley Verified Community Expert]

I’d be very surprised if concrete/aragonite mix in a reef tank was adding significant alk after 7 years in a reef tank.

 

[GeoSquid]

I'm using the salifert test kit and I have some cheapie test strips that also confirm. My only filtration is a large refugium with macros. I'm upgrading my 180 gal to a 10ft 300+ gallon tank here in a week or so and I'm contemplating not transferring a good portion of the rock but thought I would query the group here and see what everyone thought. I dont know what else would be causing high alk.

 

[GeoSquid]

I'm using the salifert test kit and I have some cheapie test strips that also confirm. My only filtration is a large refugium with macros. I'm upgrading my 180 gal to a 10ft 300+ gallon tank here in a week or so and I'm contemplating not transferring a good portion of the rock but thought I would query the group here and see what everyone thought. I dont know what else would be causing high alk.

I'm also going back to metal halides!

 

[Randy Holmes-Farley Verified Community Expert]

A number of things can lead to alk rising over time in a tank with low alk demand. These include falling or dosing nitrate, using tap water for top off, using any pH boost products, and slow dissolution of calcium carbonate rock and sand.

Some salt mixes have alk close to the level you post.

 

[davidm777]

Just out of curiosity. You dosing All For Reef?
I think thats what made a boost in alk on my aquarium for months.

 

[GeoSquid]

A number of things can lead to alk rising over time in a tank with low alk demand. These include falling or dosing nitrate, using tap water for top off, using any pH boost products, and slow dissolution of calcium carbonate rock and sand.

Some salt mixes have alk close to the level you post.

I'm not and haven't dosed anything in at least 2 years, maybe 3. All soft corals in my tank now. I use RODI to top off and real ocean water for water changes. I've tested the ocean water and its about an alk of 8. Only think I can think of if dissolution of something. I used to have some stonies years ago but had a plague of bubble tips kill them all. Then had a large clown tang eat all of those. Now, anytime I try a coral that would help suck alk they just slowly die. I think their dying because my alk is so high.

 

[Randy Holmes-Farley Verified Community Expert]

I'm not and haven't dosed anything in at least 2 years, maybe 3. All soft corals in my tank now. I use RODI to top off and real ocean water for water changes. I've tested the ocean water and its about an alk of 8. Only think I can think of if dissolution of something. I used to have some stonies years ago but had a plague of bubble tips kill them all. Then had a large clown tang eat all of those. Now, anytime I try a coral that would help suck alk they just slowly die. I think their dying because my alk is so high.

I would not presume 14 dKH kills corals. Red Sea Coral Pro has all close to that level(12 dKH).

But if you want it lower, you can drop the alk in your water change water as low as you want with sodium bisulfate.

 

[GeoSquid]

I would not presume 14 dKH kills corals. Red Sea Coral Pro has all close to that level(12 dKH).

But if you want it lower, you can drop the alk in your water change water as low as you want with sodium bisulfate.

Yah, maybe its not the dkh. I have a lot of soft corals and leathers and I donr run carbon.