Purple Up?

[Wjcastiglione]

So - I bought 22 lbs of live rock, it's pretty porous and fills my 29g pretty sufficiently, however - the rock is pretty white. and I want it to be that pretty purple color and ofcourse I want it right now. How well does purple up work? Is it worth the money?

[jedimasterben]

No.

[CrazyEyes]

Hell no it's not. Light, Calcium and magnesium is all you need. You'd be better off finding a small piece of LR with some on it to seed it. However some tanks don't get coralline and some can't stop it.

[slowngreen]

Good salt and light can give you tons of "purple". I had it so much in my 40b that I had to razor blade it off the glass every couple weeks. Just be patient and hopefully you will get it.

[CrazyEyes]

fwiw, in all my tanks I've used regular IO salt and couldn't keep the damn coralline off the glass/acrylic.

[rwalsh156]

Yes, it will work but not instantly like most people expect it to. One of the engineers I work with actually worked with Caribsea when the formulated the product. I used him the same question when I started my tank. PurpleUp is basically a suspension of finally ground aragonite. It works by adding Calcium, Alk, and Magnesium to the system. Bad thing is, they don't give any indications on concentration, which can lead to overdosing (especially with Calcium and Alkalinity).

 

If you have some bulk rock, this is what I would do. Paint the bulk rock with one or two coatings of PurpleUp and allow it to thoroughly dry. Then add it to the tank. If done correctly, the PurpleUp should bind to the bulk rock, adding a thin layer of aragonite, which will promote the coraline growth. Again, it will not be instant but it should help jumpstart things.

 

Hope that helps.

[4x5]

If you really want to get Coralline going in your tank just scrape some from a piece of live rock into the water column. Once it's growing it takes off really fast.

[BlndFshNoIz]

Except that you are forgetting that the pH has to be low enough for the aragonite to dissolve in order to be available and if the pH is low enough your tank is pretty much gone.

[jedimasterben]

If you have some bulk rock, this is what I would do. Paint the bulk rock with one or two coatings of PurpleUp and allow it to thoroughly dry. Then add it to the tank. If done correctly, the PurpleUp should bind to the bulk rock, adding a thin layer of aragonite, which will promote the coraline growth. Again, it will not be instant but it should help jumpstart things.

Define 'bulk rock'. If you mean dry live rock, then it is already aragonite (which is another name for calcium carbonate).

[farkwar]

Except that you are forgetting that the pH has to be low enough for the aragonite to dissolve in order to be available and if the pH is low enough your tank is pretty much gone.

 

Thats not really true.

 

You can have a local, small, at molecular level pH that is 6.5(whatever) right over here by these few Calcium Carbonate molecules, and dissolve them.

 

While the total solution has a pH of 8.2.

 

Thats how it buffers.

[farkwar]

Anyway, Ive always been a critic of Purple Up. Without trying it.

 

I bought a bunch of Premium Select Fiji Live Rock overnighted from LA.

 

Same story. Dead rock, again, total false advertising. Trying CPR on it in a Sterilite bin, testing a bottle of Purple Up on it.

 

Messy stuff. After wasting $160 on overnighted dead rock, $16 is not going to hurt.

[Deleted User 8]

Thats not really true. You can have a local, small, at molecular level pH that is 6.5(whatever) right over here by these few Calcium Carbonate molecules, and dissolve them. While the total solution has a pH of 8.2. Thats how it buffers.

 

Can you please explain further? How do you know, or how would one determine the pH at the molecular level? Is it always at a level that allows the aragonite to be dissovled? If this is true, our aragonite rock, and reefs in the ocean, would eventually dissolve.

 

That is how what buffers?

 

Buzz

[BlndFshNoIz]

http://www.advancedaquarist.com/2002/7/chemistry

[Deleted User 8]

I just stumbled upon an old post at ReefCentral by MCSaxmaster. Notice the bit at the end about zones of lower pH, but the CaCO3 recrystalizing if it leaves that zone into a higer pH area.

***************************************

 

"This question is not entirely answerable without specifiying other characteristics. Substances, whether aragonite, calcite or whatever do no dissolve based on pH or temperature or whatever else, but rather as a result of the degree of saturation of the solution (supersaturated vs. saturated vs. undersaturated).

In other words, we can't know whether or not aragonite will dissolve bases just on the pH--we need to know several other water chemistry parameters. Temperature and salinity have small effects on solubility. Calcium concentration and carbonate concentration each have a big impact. Carbonate concentration is controlled largely by the amount of dissolved inorganic carbon and the pH (lower pH means relatively less carbonate).

So, when pH drops aragonite or calcite begin to dissolve not as a response to the pH, but instead as a response to the carbonate concentration.

At a salinity S = 35 and temp T = 28 C in NSW if we set the alkalinity to 2.3 meq/kg, which would be normal sea water, we'd have to drop the pH to 7.52 or lower to get dissolution of aragonite. Calcite would be supersaturated down to a pH of 7.33 and then would begin to dissolve.

If we have higher alkalinity of say 4 meq/kg, which is normal in a lot of reef tanks, we will have more DIC and hence more carbonate at a given pH. Hence, to get dissolution of aragonite the pH needs to be at or below 7.27 and for calcite pH needs to be at or below 7.08.

If we want to dissolve lots of aragonite such as in a calcium reactor and therefore will have water with very high levels of calcium and alkalinity then we need to start getting down into the 6's to keep carbonate in sufficiently low supply.

So, at a pH of around 8.0 CaCO3 as aragonite or calcite isn't going to dissolve significantly (unless we subject it to crazy high pressure), and in fact we should see net precipitation. It IS possible to have locally low pH environments though. For example, the tank might have a pH of 7.8 while deep in a sandbed the pH might be 7.4 or something like that. In that case we'd see net dissolution, but the CaCO3 could recrystallize before leaving the sand bed. Also, dissolution will be so slow at that level it's going to be pretty much a drop in the bucket."

[farkwar]

 

How do you know, or how would one determine the pH at the molecular level?

Heisenberg, you can't. Thats why I wrote (whatever). It could be 2.7 or 1.1, 13.2, know one knows.

 

Is it always at a level that allows the aragonite to be dissovled? If this is true, our aragonite rock, and reefs in the ocean, would eventually dissolve.

No. They do eventually dissolve.

 

Well, ya sorta. You mean at the level you can see and test for pH? Or at the level where hydrogen ions are next to a solid CaCO3 molecule? Anyway, theoretically, reactions are "possible" except at absolute zero.

 

Baste your aragonite live rock. Besides poop, what else do you see come off the rocks?

 

That is how what buffers?

Carbonate, Bicarbonate. HCO3.

 

http://en.m.wikipedia.org/wiki/Buffering_solution

[farkwar]

Also, dissolution will be so slow at that level it's going to be pretty much a drop in the bucket."[/Quote]

 

Exactly. Analogy.

 

But like drops of rain.

 

On marble statues or architecture, CaCO3. Which is way more dense than the CaCO3 we use in our tanks.

 

Not every drop of rain is going to be burn-through-your-skin nitric acid. Most drops of rain, or droplets in a mist will be pH neutral.

 

But every once in a while, one drop is just acidic enough to make a small reaction, a small etch in the marble.

 

Over time, you can see the effect.

[k4ndyk1ng]

No.

Solid