The word on Phosphates

[mossanimal]

To add on, this can get tricky since some corals will not care about elevated residual po4 and some will care a lot. Generalizing about "corals," or "SPS" or whatever is not helpful. I mostly have acropora in my tank and there are some that will suffer, stop growing and die back at .1, or so, where others can go to 1.0 and beyond.

I measure about 1-3 (sometimes up to 5 on occasion) ppb on Hannah Ultra low Phosphorous checker. When I had a Hach Total P kit which tests all kinds of phosphates and phosphorous sources, not just orthophosphate, the numbers were 5-10x higher than this. These other forms get phosphorous to your corals too.

Just testing po4 does not tell you the whole story and can be fools gold, IMO. All that it tells you for sure is that you have a surplus.

I, for one, see MUCH faster coralline growth with lower no3 and po4 levels... much faster. Chaeto grows faster for me too, but it will still grow in higher level tanks. I do not experience true acropora burnt tips because 1-3ppb of po4 and .1 no3 are not Ultra Low... just ocean type of level - if you get below these, usually needing chemicals and media, then the skeletons can calcify so fast that they can outgrow organic tissue.

Feed your fish a lot, export a lot. Keep residual levels fairly low if you want to keep any coral at any time, or choose corals that thrive in the levels that you want to keep - find your zen place for cost/effort of export. The rest will be OK.

I appreciate all of this. I’ve learned more from this one post than all the online reading and research that I’ve done.

As to the DOM/DOC… I always figured that algae was just a space competitor. The link to pathogens and localized oxygen depletion is fascinating. I’m not sure what role this plays in an aquarium, but it’s given me a whole new perspective on what wild corals are facing. I was in the BVI a few years ago and did not observe a single living reef cruising through the islands.

 

[ナイトコア猫]

Yeah! I use it as a focus for teaching ecosystems and marine biology to my 5-8 grade students. It's awesome.

It must be great to be a student in your class!

 

[mossanimal]

It must be great to be a student in your class!

They love it. And it’s great that I can pull out so many invertebrate phyla for direct observation whenever I want. Keeping petri plates in my sump for looking under the scope is pretty amazing too.

 

[TheCa11ousOne]

The reasons for corals to grow or not grow are very complex and include environmental conditions different from what they were used to and microbial issues in tank microbiomes as well as individual coral microbiomes. From what I've seen in others and my own systems it can take weeks to months and even years for a coral to acclimate and start growing.

Unfortunately the recommendation to keep PO4 low (in ppb) was espoused by "gurus" that didn't look at the research or what researchers were observing and it became the dogma still spouted by some. FWIW .03 mg/l is the threshold level to prevent phosphorus limitation in corals, identified by researchers at Southampton University in England using corals maintained in an aquarium for about a decade. .3 mg/l is what corals are subjected to with upwelling in the ocean. .5 mg/l might be acceptable for some as acros have been shown to increase growth up to this level. .9mg/l is the level the Steinhart Aqaurium's ex situ sexually reproduced acro colonies are being grwon out with. Rich Ross's (who's part of the team at Steinhart) has his acro dominate mixed reef sitting at 1.8 mg/l, his tank can be seen at the beginning of his MACNA presentation on phosphate. You can see his current levels as well as some cool videos of corals spawning in his thread.

ALso, what hasn't been pointed out until teh last few years is we are dealing with a lot more than just phosphate or Dissolved Inoragainc Pohsphorus or DIP. Reef systems have Particulate Organic Phosphorus or POP and Dissolved Organic Phosphorus or DOP, niether we can test for. As is evident in this figure from this paper on phosphorus cycling in corals it's possible depending on the foodwebs in a system corals may in fact be the source of phosphates as they process POP and DOP



If you're interested into looking into the microbial stuff here's some links:

"Coral Reefs in the Microbial Seas" This video compliments Rohwer's book of the same title (Paper back is ~$20, Kindle is ~$10), both deal with the conflicting roles of the different types of DOC in reef ecosystems. While there is overlap bewteen his book and the video both have information not covered by the other and together give a broader view of the complex relationships found in reef ecosystems


Changing Seas - Mysterious Microbes


Microbial view of Coral Decline


Nitrogen cycling in hte coral holobiont


BActeria and Sponges


Maintenance of Coral Reef Health (refferences at the end)


DNA Sequencing and the Reef Tank Microbiome

Thank you SO MUCH for the time you took to write this out and share. I have been running myself ragged about Phosphate levels. I'm readjusting my approach thanks to your shared research!