Is it the food or is it the nitrate/phos?

[reefgeezer]

OK, there are lots of threads that talk about minimum nutrient levels required to keep corals healthy and well colored. .02-.04 ppm of Phosphate and like .5-2 ppm of Nitrate are often quoted. For discussion purposes, I question this seemingly accepted requirement. Here's a couple of questions to challenge the notion.

1. Even when nutrients aren't reported to be present by even the most sensitive test kits, aren't they still present at transient levels if biological processes are occurring in the tank? Why can't corals take advantage of these nutrients?

2. Could it really be that feeding enough (for both fish or corals) to keep corals healthy and colorful might drive nutrients up a little? If so, could we have deduced the need for elevated nutrients rather than the need for more food?

 

[elegance coral]

I think you pretty much got it.

You don't need to maintain X amount of inorganic PO4 in the water, if your corals are getting what they need from the organically bound PO4 in the food it's receiving.

I run my reef with undetectable PO4 but my sticks are colorful and grow like weeds.

 

[tmz]

In a fed tank there is likely little chance of a phosphate deficiency . Deficiencies do happen even in fed tanks ,however, particularly when removers like GFO (which also removes some organic phosphate and other things beyond iorganic phospahte ) and/or lanthanum chloride are in use.

Natural reefs average around 0.1ppm . Surface water is lower 0.005 after it's filtered through the corals on it's way to the surface. btw.

In my case even without removers and heavy feeding measurable PO4 around 0.02ppm to 0.04ppm ( given the limits of test accuracy) seems best for coral vibrancy and algae control. Undetectable brings on some paling .

There are a number of cases with undetectable PO4 reported where coral's begin to bleach and recover when PO4 is allowed to rise a bit.

Then too, there are some tanks that do well at significantly higher PO4 levels and many running at undetectable levels; some with and some without specialized supplements.

So; I don't think one can set a generalized requirement for inorganic PO4 or NO3. We do know all living things need phosphate and nitrogen along with a number of other elements like : carbon, potassium, iron etc.

0.2 ppm is the level in reef surface waters for NO3 and works well for my tanks for a variety of corals. The presence of adequate nitrogen also helps PO4 uptake by heterotrophic bacteria when organic carbon dosing which is likely enriching the food web as well as facilitating nutrient export.

 

[CHSUB]

In a fed tank there is likely little chance of a phosphate deficiency . Deficiencies do happen even in fed tanks ,however, particularly when removers like GFO (which also removes some organic phosphate and other things beyond iorganic phospahte ) and/or lanthanum chloride are in use.

Natural reefs average around 0.1ppm . Surface water is lower 0.005 after it's filtered through the corals on it's way to the surface. btw.

In my case even without removers and heavy feeding measurable PO4 around 0.02ppm to 0.04ppm ( given the limits of test accuracy) seems best for coral vibrancy and algae control. Undetectable brings on some paling .

There are a number of cases with undetectable PO4 reported where coral's begin to bleach and recover when PO4 is allowed to rise a bit.

Then too, there are some tanks that do well at significantly higher PO4 levels and many running at undetectable levels; some with and some without specialized supplements.

So; I don't think one can set a generalized requirement for inorganic PO4 or NO3. We do know all living things need phosphate and nitrogen along with a number of other elements like : carbon, potassium, iron etc.

0.2 ppm is the level in reef surface waters for NO3 and works well for my tanks for a variety of corals. The presence of adequate nitrogen also helps PO4 uptake by heterotrophic bacteria when organic carbon dosing which is likely enriching the food web as well as facilitating nutrient export.

well said..

 

[tmz]

could we have deduced the need for elevated nutrients rather than the need for more food?

Food is necessary even if inorganic nutrients are high.

Most corals are mixotrophic to a degree; they need a source for carbon beyond what photosynthesis can do with CO2. Some soft corals and lps may rely on photosynthesis for somewhere around 80% of their needs for carbon with the rest via absorbtion of organics from the water or direct feeding; while, an acropora may meet 95% of these needs need via photosynthesis but still needs the other 5%.

Most of the phosphate and bound nitrogen in food ends up in the water as animals eating it expel it as organic and inorganic waste. So, in a fed tank there is likely some soluble reactive phosphate and nitrogen available unless aggressive export measures take it out before it's available to the corals.

 

[snorvich]

Some great answers from TMZ. Thanks Tom.

 

[tmz]

You are welcome.

 

[Nano sapiens]

Most of the phosphate and bound nitrogen in food ends up in the water as animals eating it expel it as organic and inorganic waste. So, in a fed tank there is likely some soluble reactive phosphate and nitrogen available unless aggressive export measures take it out before it's available to the corals.

That is a good explanation as to why a tank that is regularly fed, but has very low phosphate and nitrate with moderate export measures, can still have healthy, colorful corals. A tank that is not fed often would likely do better with somewhat higher phosphate and nitrate levels to help compensate (up to a point).

 

[reefgeezer]

Thanks everyone. Ok so... pardon my simplistic, non-scientific thought processes... but if:

1. Nitrogen/Phosphorus (in some form) is required for life; and
2. Organic compounds contain nitrogen/phosphorus (in the correct form); and
3. Corals absorb or otherwise consume organic compounds to some extent and in doing so obtain the nitrogen/phosphorus needed; and
4. Nitrogen/phosphorus bound in organic compounds is not detectible using hobby grade test kits.

Then...

Is it possible that organic levels determine coral health and coloration rather than the observed inorganic nutrient levels? That might explain why coral health and nutrient levels can't be directly correlated.

 

[ca1ore]

Nothing to argue with here - and I love to argue

 

[reefgeezer]

Nothing to argue with here - and I love to argue

Man, what's RC coming to if you can't start an argument? :fun2:

 

[ca1ore]

Just the general decline of western civilization :lol: The KEY is to argue just enough to get the other guy banned but not yourself.

 

[reefgeezer]

Maybe Tom took the wind out of everyone's sails. Thanks Tom.:blown:

 

[CHSUB]

an acropora may meet 95% of these needs need via photosynthesis but still needs the other 5%.

while not wrong, most up to date info suggests acropora need as much as 50% of their food from capture.

 

[snorvich]

Just the general decline of western civilization :lol:

We just need more barbarians.

 

[tmz]

I'd like to see the"up to date info" in context if you can point to link. I certainly think feeding them is useful for a variety of nutrients and elements ; not sure they need to 50% from capture vs absorbtion.

Note the context of my comment is:

their need for carbon

 

[reefgeezer]

Note the context of my comment is:

their need for carbon

Context is not good for arguments! :spin2:

Anyway... What would Acros "eat" to provide the portion of their nutritional needs not supplied by photosynthesis? I ask because I think this is exactly where I always see color & health of corals most discussed. So, and again, pardon my simple mind... if it's not nutrients but something else... specifically with Acros and the like... what is consumed & how?

 

[tmz]

Thanks everyone. Ok so... pardon my simplistic, non-scientific thought processes... but if:

1. Nitrogen/Phosphorus (in some form) is required for life; and
2. Organic compounds contain nitrogen/phosphorus (in the correct form); and
3. Corals absorb or otherwise consume organic compounds to some extent and in doing so obtain the nitrogen/phosphorus needed;

Maybe not all they need; they do absorb inorganic phosphate and nitrogen and other elents and compunds. Some corals don't even exhibit a feeding response.




Then...

Is it possible that organic levels determine coral health and coloration rather than the observed inorganic nutrient levels? That might explain why coral health and nutrient levels can't be directly correlated.

In excess or paucity organic C,a nutrient , levels can effect coral health even for highly photosynthetic corals which produce it in bunches using light and CO2 to produce carbohydtaes. Food adds it too along with a wide range of elements and compounds( iron. potassium. iodine, managnese and so on) not just carbon, phosphorous and nitrogen ; a deficiency or excess in some of them can also account for coral health and vibrancy.

This article may be of interest:

http://www.advancedaquarist.com/2013/12/aafeature

 

[reefgeezer]

Thanks Tom. I read the article you linked. So corals may need some inorganic nutrients. I got that.

Now... Specifically in SPS corals and where "consumption" of organic nutrients is not sufficient, can the required inorganic N & P be derived from transient levels that might not show up in a test?

 

[CHSUB]

I'd like to see the"up to date info" in context if you can point to link. I certainly think feeding them is useful for a variety of nutrients and elements ; not sure they need to 50% from capture vs absorbtion.

Note the context of my comment is:

their need for carbon

maybe i was being a little garrulous. however, you right it's old info, here's some, "Just to put some numbers on things, as aquarists tend to resist tooth and nail the idea that these corals eat things and need to be fed, Bythell (1988) found that Acropora palmata (the ultimate "SPS" coral) gets 70% of the nitrogen it needs for health, growth and reproduction from eating things such as zooplankton and particulates."