Does Controlled Phosphate Leaching from Live Rock Hurt SPS Corals?

[sgrosenb]

Hi all,

I have battled keeping phosphates low for a while now. If left unchecked, they rise to 0.3 and beyond. My tank is 3 years old and my live rock came from KP Aquatics (which comes directly from the ocean), kept in water the whole time, right into my tank which caused little to no cycle.

I'm sure that the rock has PO4 in it, as I have lowered my feeding and addition of nutrients into the the tank and PO4 still increases. I have a fuge that grows chaeto like a weed, a powerful skimmer, and I do 20% water changes weekly. Still it creeps up without additional removal.

I dose Lanthanum Chloride (into a 5 micron filter sock with good flow) and keep feeding my fish healthily - with that routine I'm able to maintain PO4 right at 0.05ppm. I dose Nitrates to keep them rock steady at 2-3ppm.

Only problem is, my SPS corals WILL NOT GROW!!! They just sit there, somewhat colorful, and don't budge. I've had some success in the past with growth, but then it stops. Over the past 3 months or so I've had what I would call zero growth on any acros, and maybe a tiny amount of growth with some monit's. All my other parameters are spot on, including Alk at 7.8-8.0 like clockwork.

I have to believe that the PO4 is my issue, and I've read time and again that rock leaches PO4, sometime for a very, very long time. But if I'm keeping PO4 at a steady rate of 0.05ppm, would the PO4 leaching from my rock still have an adverse impact on my corals?

Any and all thoughts are welcomed. I don't have any issues with algae in the tank and like I said, everything else is great. I've done numerous ICP tests, alk and salinity tests with various kits, etc. All other parameters are what the reefing community views as spot-on.

Thanks for any insight you all have!
-Scott

 

[MnFish1]

I do not think PO4 is your issue - unless
1. Your test is not accurate
2. Curious - why are you letting it rise to .3 and then back down again - depending on how often you're doing it - that could be part of your problem

 

[sgrosenb]

Thanks @MnFish1 I don't let it rise back up, but I did a while back to see if it would stay level or if it would just continue to rise. It's been steady at 0.05 for many months. Any thoughts on what else my issue could be, if not PO4?

 

[MnFish1]

Thanks @MnFish1 I don't let it rise back up, but I did a while back to see if it would stay level or if it would just continue to rise. It's been steady at 0.05 for many months. Any thoughts on what else my issue could be, if not PO4?

I would double check all of your tests. Do you use activated carbon (could there be some coral warfare going on)? This might be the one time I would consider an ICP test - i.e. you're having symptoms - without an obvious cause?

I guess one more thing - and don't be insulted - but are you making sure you're mixing your salt correctly - some require 24 hours mixing, etc etc. many people don't think that thats important but - with 20% a week it could be?

What temperature is your tank at - is it stable? Lighting?

 

[Dburr1014]

Thanks @MnFish1 I don't let it rise back up, but I did a while back to see if it would stay level or if it would just continue to rise. It's been steady at 0.05 for many months. Any thoughts on what else my issue could be, if not PO4?

Sometimes they just need more time.
One day they may take off.

 

[sgrosenb]

Thanks all. @MnFish1 My temperature stays right around 78-79 degrees (with a chiller) as you can see below. Salinity is in check with a refractometer and Apex probe. No active carbon and all ICP tests come through with pretty much flying colors (see attached most recent one). I do let my salt mix for 24 hours so I don't think that's it, but I appreciate the thought. I won't be insulted with anything! Sometimes in this hobby it is simple things that people overlook. I'm just at a loss as to what it could be on my end...

 

[sgrosenb]

I forgot to mention lighting - I have a T5 / LED combo 4x Radion G4 at full power SPS+ for 6 hours with a 3 hour ramp up and 3 hour ramp down. I also have 4x T5 (2x BluePlus, 2x Actinic) running for 6 hours when the LED's are at full power. PAR meter shows 150 at the bottom and 400 at the top, give or take. Most corals are in 250-350.

 

[MnFish1]

I forgot to mention lighting - I have a T5 / LED combo 4x Radion G4 at full power SPS+ for 6 hours with a 3 hour ramp up and 3 hour ramp down. I also have 4x T5 (2x BluePlus, 2x Actinic) running for 6 hours when the LED's are at full power. PAR meter shows 150 at the bottom and 400 at the top, give or take. Most corals are in 250-350.

Could it be that your lighting time is too short? I run my LED's for 10 hours/day - and in the AM between 8 and 12 - a patch of sunlight lights various parts of the tank from the front. (LEDS then have a 30 minute ramp - 9 hours then a 30 minute ramp down (noon to 10PM)

PS think about the length of daylight lets say at the equator. (12 hours)

 

[sgrosenb]

Funny you say that @MnFish1 I've actually tried both. I used to have them on peak for 9 hours with a +/- 3 hour ramp up/down. Same results as I currently have. I've heard varying approaches to lighting, and I feel like I've tried a decent range and kept it there a long time with the various approaches. I'd be surprised if lighting is my issue to be honest, but I won't rule anything out.

 

[Dburr1014]

Could it be that your lighting time is too short? I run my LED's for 10 hours/day - and in the AM between 8 and 12 - a patch of sunlight lights various parts of the tank from the front. (LEDS then have a 30 minute ramp - 9 hours then a 30 minute ramp down (noon to 10PM)

PS think about the length of daylight lets say at the equator. (12 hours)

Funny you say that @MnFish1 I've actually tried both. I used to have them on peak for 9 hours with a +/- 3 hour ramp up/down. Same results as I currently have. I've heard varying approaches to lighting, and I feel like I've tried a decent range and kept it there a long time with the various approaches. I'd be surprised if lighting is my issue to be honest, but I won't rule anything out.

My tank has been on 4 hours ramp up, 4 hours peak, 4 hours down for years. I really don't think that is an issue here. I have about 300/350 par at the top.

 

[Clownfishy]

I cannot comment on your coral growth but I can sympathise with your phosphate raising and coming to the conclusion its the rock. I have the same problem with phosphate and it does not matter what amounts I feed, my phosphate just continues to rise and very quickly. I dose 3.2ml of NOPOX a day into a 75l (19.8 gallon) nano and that only keeps my phosphate at 0.13. It is leaving a scum on the top of the water and I have to clean the bacteria off the glass every few days. Like you, I experimented and stopped dosing NOPOX to see what happend and my phosphate shot up to 0.6. Well it went higher but the Hanna Phosphorous test kit cannot read any higher!

Like you, I can only think this is coming from the rock and I do not want to worry you, but my rock is about 6 years old and still leaching. In fact, I would say it is getting worse ever since I started dosing Brightwell Clean bacteria as I am assuming this is cleaning the rocks causing phosphate to escape further but that is just a hypothesis.

I am not seeing a slow down in my SPS coral growth. My LPS corals are suffering STN but I dont think that is the phosphate levels as they have always been high. The STN started after a 24 hour power cut and it is only affecting my LPS corals.

I feel your pain and I think I am at the point where I will continue dosing bacteria to clean the rock for a while longer but if nothing changes after that, I will bin this rock and replace it with something else.

I hope you find a solution

 

[sgrosenb]

@Clownfishy that's a bummer but unfortunately I've read the same thing many times - that some rock can have PO4 leech (or as @jda puts it - "unbind") for years. I'm just wondering if there is any indication that the leeching could hurt SPS corals so long as the PO4 is left in check.

I, too, have considered buying new rock, removing all the PO4 in a bin, and then changing out my current rock with that. Only problem is I'm concerned that all the good bacteria, etc that is in my current rock is beneficial, and removing that could be detrimental in and of itself.

 

[Clownfishy]

@Clownfishy that's a bummer but unfortunately I've read the same thing many times - that some rock can have PO4 leech (or as @jda puts it - "unbind") for years. I'm just wondering if there is any indication that the leeching could hurt SPS corals so long as the PO4 is left in check.

I, too, have considered buying new rock, removing all the PO4 in a bin, and then changing out my current rock with that. Only problem is I'm concerned that all the good bacteria, etc that is in my current rock is beneficial, and removing that could be detrimental in and of itself.

That is exactly why I have not changed my rock because of the bacteria but it is getting to a point where I am tired of dosing so much NOPOX. Every now and then I think the leaching will stop but after all these years, I think I am just being naive. It must have an effect on the corals ability to build their skeleton structures but I cannot explain why my SPS growth is OK. Maybe it would be much better without such a high phosphate level.

 

[MnFish1]

My tank has been on 4 hours ramp up, 4 hours peak, 4 hours down for years. I really don't think that is an issue here. I have about 300/350 par at the top.

so - you dont think that 1/2 the light that you're using makes a difference?

 

[MnFish1]

IMHO - the phosphate is coming from input not the rock. I feed my fish once/day - I skip a day occasionally - with no adverse effects

 

[Dburr1014]

so - you dont think that 1/2 the light that you're using makes a difference?

I think coral needs only so much of peak light a day. If they get to much they may get stressed.
The sun may be up for 12 hours a day but how long does it sit over any particular coral? Sunup its on one side, sundown it's on the other side of the coral. Our lights are directly over the tank for the whole time the light is on. I just give them varying intenses over the 12 hours.

 

[MnFish1]

I think coral needs only so much of peak light a day. If they get to much they may get stressed.
The sun may be up for 12 hours a day but how long does it sit over any particular coral? Sunup its on one side, sundown it's on the other side of the coral. Our lights are directly over the tank for the whole time the light is on. I just give them varying intenses over the 12 hours.

Yes - clearly - if they get too much light they get stressed. We can agree to disagree. IMHO, its fine to ramp up and ramp down - IMHO 6 hours TOTAL is too little when its being ramped up and down over the whole time. He asked what might be going on with growth - I was only giving my opinion.

 

[sgrosenb]

Thanks all. To be clear - my lights are on for a total of 12 hours - 3 hours ramp up, 6 hours full blast, then 3 hours ramp down.

I'm still curious if anyone has more insight into whether rocks releasing PO4 is detrimental to corals if the PO4 is ultimately kept steady at a level of roughly 0.05ppm.

 

[Dburr1014]

Thanks all. To be clear - my lights are on for a total of 12 hours - 3 hours ramp up, 6 hours full blast, then 3 hours ramp down.

I'm still curious if anyone has more insight into whether rocks releasing PO4 is detrimental to corals if the PO4 is ultimately kept steady at a level of roughly 0.05ppm.

I think if your keeping po4 steady @ 0.05 you should be good.
Your rocks could leach them for a long time until they reach an equilibrium.
Have you played with your no3 up or down? You said they are steady at 2/3 ppm. Or bring up the po4 closer to 0.1

 

[Dennis Cartier]

I second the suggestion to let your PO4 rise a bit to around 0.1 ppm. If you are dosing LaCl often enough, you may actually have less PO4 than 0.05 ppm you think you have. Any reacted LaCl still in the water column, if it evades your sock, will cause the Hanna checkers to register a higher reading than is actually available and usable. So letting it rise to 0.1 ppm will give you some headroom.

Also, the 20% weekly water change may be causing a bit too much fluctuation for SPS. They really need stability, and depending on how close you are matching the existing tank parameters to the new water, it may be enough to keep SPS dormant and not growing. You may want to reduce the % weekly or be extra diligent to match parameters.

Generally speaking, too much PO4 will not hurt SPS, though they will slow calcification above 0.25 ppm, but too little PO4 will stop them from growing and potentially cause STN/RTN if depleted completely.