Light, Alkalinity, Nutrients.

[Dana Riddle]

I'd like to hear your thoughts of the relationships of these 3 parameters. For example, I've seen recommendations to adjust nutrient levels upwards if running high alkalinity, which seems to defy Liebig's Law of the Minimum which states the rate of photosynthesis is regulated by the least available nutrient, not the most abundant. In other words, alkalinity, acting as the carbon source for photosynthesis, doesn't matter if phosphorus is the limiting factor. Unless you're suggesting alkalinity has an effect unrelated to photosynthesis.

 

[CodyRVA]

Currently going through this mess right now. IME running a ULNS requires lower ALK. Every time my ALK creeps up when running 0 - low nutrients I experience burning. My dimensions are also very shallow and one would consider it to generally be a high PAR system. I don't think you have to have "high nutrients" if you have high ALK, but you should have more than "detectable" levels. Testing out "0" for NO3 and PO4 with a dKH above 9 will likely result in an ALK burn. Lighting is directly connected in regards to coral consumption. Although, I will add that some corals are much more sensitive to this than others. Obviously Softies are the least affected while most SPS are heavily affected and most LPS are unaffected, but some varieties definitely are. Just my .02!

 

[Dana Riddle]

Currently going through this mess right now. IME running a ULNS requires lower ALK. Every time my ALK creeps up when running 0 - low nutrients I experience burning. My dimensions are also very shallow and one would consider it to generally be a high PAR system. I don't think you have to have "high nutrients" if you have high ALK, but you should have more than "detectable" levels. Testing out "0" for NO3 and PO4 with a dKH above 9 will likely result in an ALK burn. Lighting is directly connected in regards to coral consumption. Although, I will add that some corals are much more sensitive to this than others. Obviously Softies are the least affected while most SPS are heavily affected and most LPS are unaffected, but some varieties definitely are. Just my .02!

So, when you say lighting is directly connected in regards to coral consumption - are you speaking of alkalinity or nutrients or ???. Photosynthesis and calcification compete for bicarbonate, so when you say alk burn happens in low nutrient systems (where low N or P might limit photosynthesis), are you suggesting that the calcification process is responsible for burn? I'm still unclear on why these suggestions are made (guess I've been challenged to defend my positions for too many years.) Thanks for the response - further thoughts?

 

[CodyRVA]

So, when you say lighting is directly connected in regards to coral consumption - are you speaking of alkalinity or nutrients or ???. Photosynthesis and calcification compete for bicarbonate, so when you say alk burn happens in low nutrient systems (where low N or P might limit photosynthesis), are you suggesting that the calcification process is responsible for burn? I'm still unclear on why these suggestions are made (guess I've been challenged to defend my positions for too many years.) Thanks for the response - further thoughts?

For example, I had a PO4 spike which caused my corals to shut down (no polyp extension, browning and STN). When my corals did that it also slowed the utilization of my daily ALK dosage; this then resulted in an ALK spike. So, my corals were irritated from the high PO4, then they were super stressed from an ALK spike. I lowered my ALK and cut my lights down from 6 T5 bulbs to 2 because I noticed corals with the most direct light were mostly affected (both LPS and SPS... softies weren't affected). However, when I cut my lighting back I noticed my ALK actually went up a 1.0 dKH; that's when I had a duh moment, my corals weren't active because of I lowered my lighting and in turn my chemistry got even more out of wack.

I'm no expert by any means, just reporting my findings here, but when you say...
[QUOTE="Photosynthesis and calcification compete for bicarbonate, so when you say alk burn happens in low nutrient systems (where low N or P might limit photosynthesis), are you suggesting that the calcification process is responsible for burn?[/QUOTE]

This makes sense and would explain why my stony corals were so much more affected than my LPS and softies. The fleshy LPS were not affected, only my cyphastrea and lepto (which is why I always considered them SPS, but lets not even get into that debate).

 

[Dana Riddle]

I ran multiple frag grow-out systems in the late 90's (literally thousands of SPS.) When we installed calcium reactors, the alkalinity jumped overnight but we didn't lose any corals, although we did see some A. milleporas color up. Charles Delbeek and I debated this - he said the milles bleached, but he wasn't there. I certainly respect Charles but I did disagree on this point. But for argument's sake, if the milles did bleach, why just them and not all the others?

 

[CodyRVA]

I ran multiple frag grow-out systems in the late 90's (literally thousands of SPS.) When we installed calcium reactors, the alkalinity jumped overnight but we didn't lose any corals, although we did see some A. milleporas color up. Charles Delbeek and I debated this - he said the milles bleached, but he wasn't there. I certainly respect Charles but I did disagree on this point. But for argument's sake, if the milles did bleach, why just them and not all the others?

To that point, my first question is how much of an ALK swing are we talking about?

I commonly find myself in a debate with folks who run high nutrient systems. My only hypothesis is just like with lighting, corals can be acclimated over time to different conditions. As we all preach stability is king; those magic numbers are only reference values. Corals acclimated to "dirtier" water over time are much less susceptible to PO4 spikes which wouldn't cause the coral to shut down, thus the ALK burn never takes place. Or, could it be that coral kept in "dirtier" water are far less likely to be exposed to a PO4 spike because of the high state of nutrients in the system...?

Another note, not all SPS are created equal. It makes me wonder if running a ULNS has an unseen adverse affect on some coral. Either some are more or less forgiving to change than others and any change regardless if its nutrients or ALK will cause them to die out or it could be that there are negative long term affects on coral in ULN systems. They might be doing just fine in ULN, but over time they lose their "immunity" to higher nutrients and any sign of change yields disaster; case and point; my ORA green birds nest, supposedly one of the easies to keep corals, was the first to bite the dust when my PO4 spike occurred.

Additionally, during this whole meltdown i'm experiencing... two stylos side by side, one fine, the other is bleaching. One acro is bone white, another has simply browned out. Some died immediately and some slowly over several days/weeks. Calls into question how poor our hobbyist classification of SPS/LPS/Softies really is. And lets not forget all the other variables like lighting, flow, etc.

Looping in @Fish Werx

 

[chipmunkofdoom2]

Photosynthesis and calcification compete for bicarbonate, so when you say alk burn happens in low nutrient systems (where low N or P might limit photosynthesis), are you suggesting that the calcification process is responsible for burn? I'm still unclear on why these suggestions are made (guess I've been challenged to defend my positions for too many years.) Thanks for the response - further thoughts?

I would like to learn more about this as well. I have searched high and low, and nobody seems to understand why this happens. There also seems to be little consensus on what "burnt tips" actually means. All that we seem to know is the tips of corals seem to have white skeleton exposed when dosing an organic carbon source and running higher-than-natural carbonate alkalinity. I have not seen any explanation as to why this happens physiologically.

All of the anecdotal evidence from reefers dosing organic carbon seems to suggest that excessive nitrates and phosphates limit growth. In a system with very low nitrates and phosphates, such as one where the aquarist doses organic carbon, these nutrients appear to no longer limit growth. It is possible that carbonate alkalinity then becomes the limiting growth factor. This could help explain why running higher than natural carbonate alkalinity causes "burnt tips". If the coral is laying down calcium carbonate faster than it can grow flesh to cover the new skeleton, this could result in white tips on coral colonies. If it is true that carbonate alkalinity becomes the growth-limiting factor, this also could explain why natural alkalinity levels do not have the same effect on coral tips. When coral growth is limited by lower carbonate alkalinity, the coral has sufficient time to cover the new calcium carbonate with flesh.

This hypothesis, however, makes many assumptions. I would really like to see someone do some advanced analysis, complete with microscopy and/or necropsy, to determine what is physiologically happening when hard corals have "burnt tips" under low nitrate and phosphate conditions.

 

[mcarroll]

Every time my ALK creeps up when running 0 - low nutrients I experience burning.

Are you also running a carbon-source dosing plan?

(My theory is that burning like this is related to elevated carbon levels.)

 

[Abhishek]

I would like to share my thoughts and seek advice / suggestions.

My tank is almost all acropora with some pretty sensitive ones like purple monster. All are frags . Am running a single radium 250 lit by a M80 ballast in a hamilton comuzel 20 in x 20 in reflector and 2 reefbrite led strips. Leds on for 12 hours and halide for 10 hours.

My alk is currently steady at 7.3-7.6 as i measure everyday 3 times - 7 am (before lights), 5 pm (midway during photo cycle), 11 pm (after photocycle). Alk consumption seems high during photoperiod .
Measured PAR with Apogee PAR meter and majority of the acros are in 250-300 range with the smooth skins in 100-150 PAR .

Nutrients - high .. Nitrates around 15-20 and PO4 - 0.1-0.15. I run a skimmer only for filteration (Deltec) and dose bacteria in the form of aquaforest pro bio s and np pro . But since I feed so much (4-5 times) , i think my nitrates hardly ever come down . I tried to lower my phosphates and it didn't help much as I experienced burnt tissues at the end of only my Efflo even when ALK is below 7.5.

Other issue is with dinos. Every time I bring PO4 down to below 0.05 , I see an increase in dinos. I bring PO4 to around 0.15 and dino slowly goes away. it seems almost like i am able to replicate dino on/off situation at will by just controlling phosphates.

Other funny thing is - I dont have any visible algae in the tank . May be green coating over the glass that I manually remove everyday with magnet.

Among all of these I have found that maintaining high nutrients really help to keep my small frags color up . Every single of them hold color to some extent - some more like my Oregon Tort which is blinding blue and pink shortcake which is amazing pink , some less .

I don't know if I would ever be able to reach ULNS but seeing my acros right now and not having any algae issue except for patches of dinos here and there, am not sure if I ever want to.

But wanted to know, if such high nutrients really impacting calcification and growth. Growth is there but not explosive. But it might be due to the fact that i have mostly slow growing acros like purple monster, Oregon tort , granulosas, loripes and echinata .

The other interesting thing is flow - In my small 30 in x 30 in x 18 in tank am running 2 tunze 6095 , 1 icecap gyre and 1 tunze 6105 along with a seaswirl connected to my return . Before i added 6105, growth was ok but colors were not so great. Don't know if the extreme flow has impact but i feel so .

Regards,
Abhishek

 

[CodyRVA]

Are you also running a carbon-source dosing plan?

(My theory is that burning like this is related to elevated carbon levels.)

I have a small CPR bio pellet reactor, never more than 1/8 of a cup of pellets at a time.

 

[Dana Riddle]

To that point, my first question is how much of an ALK swing are we talking about?

I commonly find myself in a debate with folks who run high nutrient systems. My only hypothesis is just like with lighting, corals can be acclimated over time to different conditions. As we all preach stability is king; those magic numbers are only reference values. Corals acclimated to "dirtier" water over time are much less susceptible to PO4 spikes which wouldn't cause the coral to shut down, thus the ALK burn never takes place. Or, could it be that coral kept in "dirtier" water are far less likely to be exposed to a PO4 spike because of the high state of nutrients in the system...?

Another note, not all SPS are created equal. It makes me wonder if running a ULNS has an unseen adverse affect on some coral. Either some are more or less forgiving to change than others and any change regardless if its nutrients or ALK will cause them to die out or it could be that there are negative long term affects on coral in ULN systems. They might be doing just fine in ULN, but over time they lose their "immunity" to higher nutrients and any sign of change yields disaster; case and point; my ORA green birds nest, supposedly one of the easies to keep corals, was the first to bite the dust when my PO4 spike occurred.

Additionally, during this whole meltdown i'm experiencing... two stylos side by side, one fine, the other is bleaching. One acro is bone white, another has simply browned out. Some died immediately and some slowly over several days/weeks. Calls into question how poor our hobbyist classification of SPS/LPS/Softies really is. And lets not forget all the other variables like lighting, flow, etc.

Looping in @Fish Werx

We were beta testing some of Knop's giant calcium reactors (not sure if these monsters ever made it to market) and, if my recollection is correct of circumstances some 20 years ago, the dKH jumped about 2 full units (that is, ~7 to 9) overnight. We didn't see any stress reactions (polyp withdrawal, mucus production, bleaching, etc.) My point is that we didn't lose any of perhaps 20 coral genera (hundreds of frags, perhaps a 100 species) we had in this system. All I am suggesting is that a sudden jump in alkalinity didn't cause any adverse effects that we could determine visually, and certainly no tip burning. Do I recommend doing this - of course not. But we did and it was part of our learning curve.

 

[CodyRVA]

We were beta testing some of Knop's giant calcium reactors (not sure if these monsters ever made it to market) and, if my recollection is correct of circumstances some 20 years ago, the dKH jumped about 2 full units (that is, ~7 to 9) overnight. We didn't see any stress reactions (polyp withdrawal, mucus production, bleaching, etc.) My point is that we didn't lose any of perhaps 20 coral genera (hundreds of frags, perhaps a 100 species) we had in this system. All I am suggesting is that a sudden jump in alkalinity didn't cause any adverse effects that we could determine visually, and certainly no tip burning. Do I recommend doing this - of course not. But we did and it was part of our learning curve.

Interesting... a few thoughts.

First, what was the duration getting from 7dKH to 9dKH? If you end the day at around 9 dKH and early morning you're at 7dKH... how long was the system at (8)+- dKH for example.

Another question... do ALK swings during non photosynthetic periods (night time) cause as much harm to corals as they would during a photosynthetic period (day time). Can you in fact have a reasonable range, say up to a 2-3.0 dKH swing during non photosynthetic periods without tissue damage?

It would be really interesting to see a systems ALK tests hourly over the course of say 36-48 hours and compare systems that carbon dose, those who don't, those who run high nutrients and those that run ULNS.

 

[mcarroll]

If the coral is laying down calcium carbonate faster than it can grow flesh to cover the new skeleton

They have recently proven that corals "lay down" skeleton from the inside via their tissues...so I don't think that explanation will ultimately hold.

I have a small CPR bio pellet reactor, never more than 1/8 of a cup of pellets at a time.

I don't know if you're in a position to experiment (or if this is the thread for it....PM me!) but if you eliminate that C source and then balance your N and P via ferilizer (e.g. potassium nitrate/potassium phosphate), I think you'd have no further "tip issues". (And maybe even no continuing need for the C source at all.)

 

[CodyRVA]

I don't know if you're in a position to experiment (or if this is the thread for it....PM me!) but if you eliminate that C source and then balance your N and P via ferilizer (e.g. potassium nitrate/potassium phosphate), I think you'd have no further "tip issues". (And maybe even no continuing need for the C source at all.)

My system is currently in disarray so it wouldn't be worth testing anyways, but honestly the amount of pellets I have running at any given time is a joke. It has got to be only barely making a difference. I used to not run GFO at all either until I ran into PO4 troubles after relocating the system long distance.

 

[revhtree Verified Admin]

Nice discussion!

 

[reeferfoxx]

Aren't burnt tips just a sign of low or expelled zoox? If the idea that higher alk produces a faster rate of calcification, it would take time for the appearance of "burnt tips", no? Plus little to no nutrients wouldn't allow for the propagation zoox.

FWIW I've always seen a coral reaction to alk fluctuations. Especially from low N and P in regards to alk levels. However, my system wasn't cycled with live rock. Only 100% dry rock. I think live rock has ways of supplying nutrients when nutrients aren't supplied.

 

[Dana Riddle]

What are we suggesting re: carbon dosing? That it acts as a carbon source for photosynthesis? That the natural Redfield Ratios of 117 C: 17 N: 1 P getting out of line are responsible?
I'd like to get this back on track - why do some recommend raising nutrient levels to keep them inline with a given alkalinity level? (I get private email from hobbyists about this, but can't figure out how this recommendation got started, much less how it is grounded in science.) This we do know:
Redfield Ratios, when out of whack, can cause outbreaks of organisms (usually 'bad' things.) For example, high organic carbon can cause outbreaks of a filamentous bacteria in wastewater treatment systems. A standard test - biochemical oxygen demand - is usually a good indicator of carbon available for bacterial consumption, yet I have never been able to measure a BOD of more than a fraction of a milligram per liter.
Ortho-phosphate is a poison to the calcification process - it combines with calcium to form insoluble apatite. Increasing ortho-P (which our test kits measure) would slow down calcification. By the same token, decreasing ortho-P would limit algae/zooxanthellate growth. So, calcification and photosynthesis are not competing processes.
On the other hand, photosynthesis and calcification are competitors for inorganic carbon in the form of carbon dioxide or bicarbonates.
So, back to the original question - why do we juggle nutrient levels according to alkalinity?

 

[reeferfoxx]

So, back to the original question - why do we juggle nutrient levels according to alkalinity?

For best coral coloration

 

[jsker]

;Stig

 

[reeferfoxx]

Forgive me if this sounds insulting(definitely not ment to be) but the 90's seemed more about "how to keep coral alive" whereas the post millennial group of reefers "how to get the best colors". I think we've left the dark ages and entered a new realm of how to get the best colors.