Reef Chemistry Question of the Day #285: Aragonite vs Calcite

[Randy Holmes-Farley]

For sure I am not recommending anyone specifically target 1 ppm phosphate. I generally recommend 0.03 to 0.1 ppm, with above the range better than below it.

The question is how much effort and angst should a reefer expend if the tank is currently at 0.2 or 0.5 ppm. Is it worth lowering?

I agree that there are many more aspects to nutrients than calcification, as you mention. Color, algae, etc. All of these may be reasons to elect a specific target range, though that range may then vary a lot depending on the organisms and the aquarist's goals.

 

[Thales]

I think the interpretation that some corals died off due to phosphate has to be conjecture rather than a demonstrated fact since one cannot know why they died and many folks lose corals over time. It certainly may be a correct conjecture, however.

Let's see if we can get his current thinking: @Thales

I can't say anything died due to phosphate levels - stuff has died in my tank, but stuff dies in every tank regardless of the reefing philosophy. I ran a lot of tanks for 10 years, and for roughly the first half I kept nitrate and phosphate low, and had stuff die at about the same rate in all cases regardless of n and p levels. Folks in the same facility I worked in that kept on top of n and p, had corals die, often at rates higher than mine. Not everything does well in all tanks. I have some almost 20 year old corals in my display. I have a bunch that are over a decade old. I can't say phosphate had anything to do with any of the death though people want to say it was - it certainly didn't stop me from raising baby acros in the same water (and yeah, I got phosphate levels of .9 mg/l into the lit for raising coral - reviewer 2 was grumpy!)
I didn't recommend people do what I do as a matter of cya because people force recipes out of reef keeping philosophies - I think that isn't great for the animals or the reefer and I don't want that kind of drama, so try to keep distance and recommend people make their own decisions.
In the 2014 talk, I showed about 10 tanks with high nutrient levels, so N was more than 1 then, and is more now.
I lowered my nitrate and phosphate levels over several years to see if there seemed to be any difference in animal life, health, or growth at lower levels, and there seems to be no difference. Also to see if was easy to do. Some stuff grows fast, some stuff grows slow. Last time I tested n, 14 mg/l and phoshapte between .1 and .2 mg/l (depending on which test you trust), those tests were in October 2023. Below, is a pic of the tank from about two weeks ago, I keep meaning to test, but can seem to find a good reason to spend the time doing testing. I also spawned acros, raised larvae and am raising settlers in the same system, and I did similar in 2020 when the levels were n 50mg/l and p04 .97 mg/l.
It will be interesting to see what I do when I run out of Lanthanum Chloride in 5 years, or when I can't easily get saltwater, I am sure I'll let the numbers rise because, well, work. I do find it amusing that the recommended levels of n and phosphate 10 years ago were like 5 and .03, but now they are like 20-30 and .1-.2. And even funnier that people are dosing nitrate and phosphate because I joked about the possibility in 2014 and got a big laugh.

IIRC the amounts that the studies show decreased growth are like less than 10% slower, so it seems to me the juice of lowering n and p may not be worth the squeeze.

For fun, some baby A. millepora and baby urchin from my syste a few weeks ago - my last name in my watermark is about 1mm for scale

 

[Randy Holmes-Farley]

Congrats on the babies and thanks for the update!

 

[biom]

For sure I am not recommending anyone specifically target 1 ppm phosphate. I generally recommend 0.03 to 0.1 ppm, with above the range better than below it.

The question is how much effort and angst should a reefer expend if the tank is currently at 0.2 or 0.5 ppm. Is it worth lowering?

I think the answer is:
No, if it is an established tank and there are no problems that could be could be high phosphate related - coral bleaching or discoloration, algae... there is no reason to start lowering .