Might purple up have a positive effect other than adding (inert) alk / Ca?

[UK_Pete]

I've read a lot of anecdotal reports from people who swear by purple up and also Randys (negative) opinion of it, and I was wondering if it might do something else apart from add calcium carbonate. I wondered if since its very fine aragonite it might attract organics as it tries to grow larger calcium carbonate crystals once it hits the supersaturated tank water (since organics have been shown to stick to and poison calcium carbonate precipitation crystals in seawater) and build a coating of organics and hold them while it settles perhaps, for instance. Or is it compete snake oil and those who swear by it are just victims of placebo? Any experiences / science?

 

[TheChef]

it might pull heavy-metals, but I dont think any more effectively than activated carbon...and theres still the issue of exporting it from your tank. There might be a buffer quality if enough of it settles into your sandbed, but I'd still think limwater is a bigger bang for your buck

 

[Randy Holmes-Farley]

I do not know all of what is in it, but my problem with Purple Up is that the fine calcium carbonate won't dissolve. They seem to be modifying their claims relative to the past, and now are a little more circumspect on what exactly it does. So if it contains other calcium, then that other calcium might be useful, for example.

But the particles can serve other purposes, as you note, such as binding things (including phosphate) and may even provide new surfaces for coralline to initiate growth on.

 

[UK_Pete]

Thats interesting Randy, I didn't realise they changed their story now. I think I see what you mean about providing new surfaces for coralline to initiate on too. If someone wanted to try to prepare a diy version, do you think grinding up aragonite sand with a pestle and mortar would be effective, or would a precipitated form (like from addition of calcium chloride to sodium bicarbonate) be better since it would be finer?

 

[Randy Holmes-Farley]

Thats interesting Randy, I didn't realise they changed their story now. I think I see what you mean about providing new surfaces for coralline to initiate on too. If someone wanted to try to prepare a diy version, do you think grinding up aragonite sand with a pestle and mortar would be effective, or would a precipitated form (like from addition of calcium chloride to sodium bicarbonate) be better since it would be finer?

Other materials may work fine and i do not know what particles sizes might be best for that possibility. Aragamight or Kent Liquid Reactor (if they are still on the market) might accomplish the same thing with respect to new surface area (but not necessarily other dissolved additives in it).

 

[Cory]

I think it contains coralline algae spores and that's what seeds the tank.

 

[Randy Holmes-Farley]

I think it contains coralline algae spores and that's what seeds the tank.

Why do you think that? It doesn't claim to do so.

 

[Cory]

That's true it doesn't claim to do so, but their current description of how the product works doesn't seem to fit into science. They probably don't know how it works either. But my guess is ground up stones might contain spores of old corraline algae, or fresh beach sand containing it. To me this seems to be more logical than their description. But is just a guess.

 

[Randy Holmes-Farley]

OK, fair enough.

Alternatively, it may not work.

 

[UK_Pete]

Yes, it may not work as you say. But there seem to be so many people who swear blind that as soon as they start using it their tank explodes into rabid coralline growth that it seems worth at least a passing glance. I agree its unlikely that the makers know how it works if it does. If there is anything to it though, I guess someone once thought 'wonder if grinding up aragonite might make corals grow faster' and noticed that although corals didn't grow faster coralline did grow. So decided to sell it as a 'highly scientific patented product which enhances coralline growth', and put a patent application in to add apparent validity. I guess dosing kalk in a way that causes a little abiotic precip would also create new surface area woudlent it?

 

[Randy Holmes-Farley]

That's certainly a possible scenario. Not sure how much new surface kalk causes, depending on the situation.

 

[UK_Pete]

Yea I was thinking when its (kalk) added to a low flow area and pH builds up for a while, once precipitated because of the supersaturated nature of seawater I guess particles won't redissolve in that kind of situation? When you get the local milky look in an area you add a high pH form of alk like kalk, is it calcium carbonate or something else thats the visible milky precip?

 

[Randy Holmes-Farley]

Magnesium hydroxide is the transient cloudy precipitate that forms on limewater addition. Calcium carbonate precipitation is slower but irreversible.

 

[UK_Pete]

Ah thought so, I must remember that from one of your articles now you mention it I remember. Its only overdosing and snow storms that cause calcium carb precip isent it. And local precip onto surfaces that are already covered in calcium carbonate, but that probably would not work in the same way as adding new surface I guess as its easily poisoned.

 

[Randy Holmes-Farley]

FWIW, I have a lot if solid CaCO3 precipitation onto the walks of my sump where the limewater enters, but I do not know if there is particulate material also made on addition.

 

[UK_Pete]

When I used to ATO with kalk I dont remember any lasting milkyness so I guess its unlikely with the amount of kalk I would be likely to use (small tank). But your suggestion to add pure kalk seems to make sense to me. The particles will have a higher pH so will enhance precip on their surface wont they, as well as being a point source of high alk. I wondered about treating the kalk suspension I made (10g in 250ml water) with CO2 or similar to make a calcium carbonate crust on the outside of the particles to prevent them dissolving when added to the tank, what do you think? IE maybe put the suspension in a beaker on a mag stirrer for a couple of days exposed to air for instance.

 

[Randy Holmes-Farley]

Yes, precipitation on the particles before they dissolve is one reason solid dosing of calcium hydroxide isn't preferred.

Making it outside the tank is one reasonable idea if you don't want to buy something like Aragamight.

 

[UK_Pete]

Well I'm gona try dosing this kalk suspension for a bit several times a day and look out for some aragonite silt or maybe get some sand and chuck it in the ball mill once the xmas season is over. I'm not allowed enough time to go searching the local LFS for it while xmas is going on. One thing that worries me slightly about the kalk I have dosed for 1 day now, and that is I don't see any trace of it within a minute or so in the tank, so I guess its all dissolved. So maybe making it into carbonate before dosing it will be better for pH stability.

Randy, related but different question, if I wanted to dose either kalk power or aragonite dust with my peristaltic, I would need to add something to it to make it a smooth paste. I thought of gelatine, agar, and a few other gells but I think they would all negatively affect the tank. Can you think of any inert gells which might work to make powders like this flowable (without settling in the reservoir)? Also interested for the sake of feeding coral dust food with the peristaltic, although I think the putty like food I have is already preserved with high salt content so I could probably just water that down a bit to make it from a putty into a paste.

 

[Randy Holmes-Farley]

Fine powders generally settle slowly enough that if the container your pump is drawing from stays stirred, they will likely stay in suspension until delivered.

I've overdosed lime solids before when my limewater reservoir runs out and my pump sucks up more of the solids on the bottom.

 

[Big Larr]

In my experience from using purple up in the past I believe it does not have traces of coraline do to after dosing two or three bottles worth I still had zero coraline growth so I picked up some coraline scraping from a lfs and added to the tank and started dosing another bottle then the coraline growth took off quickly. Now in my current tank I have added coraline scraping and chunks of it without using any purple up and my coraline growth is there but very light and slow even though I am using a two part dose