Randy's Tank and Learn Thread

[Randy Holmes-Farley]

You made a NO3:PO4 ratio comparison of the system pre water change but only the water column post water change. Feels like apples and oranges to me, but the trend still holds even if you do it this way. With each iteration you will trend towards climbing PO4.

It all depends on where you start this thought experiment, and what is being compared to what. I don’t think we really disagree on the fundamental process, and I agree that water changes are not as effective at exporting phosphate as one may expect.

You assume there is already phosphate bound and it is going to come off. In that scenario, I certainly agree with you. A water change will not reduce phosphate as much as nitrate due to the desorption replacing some of what was lost.

But if you consider the entire process which must include how that phosphate got onto the rock, then I do not agree. Yes, the water change will still be exporting less than the 100:1 starting point/waste production ratio, but the level in the water remaining will not be higher P than the 100:1 starting point/waste production ratio. Perhaps it is the starting point meaning we disagree on. I’m think the ratio produced in the tank.

. For example, when you put that starting 100 ppm. Nitrate and 1 ppm phosphate water into contact with rock, the phosphate level declines and you no longer have that same starting level. So even though the water cha ge removes less, it’s not enough less to overcome the initial drop.

Let’s try a different approach. You said the phosphate rises with each iteration. Forever? Where would it come from? There is limited phosphate on the rock. You can’t just assume it keeps coming off without accounting for it getting into the rock in the first place.

 

[Randy Holmes-Farley]

I have found that the phosphate management strategy in my current tank dictated the foods that I feed. It was quite an endeavor to dial it in but I ultimately landed on a slightly phosphate-deficient food mix and then supplementing by dosing phosphate. As corals have grown and consumption has increased my phosphate dosing has also steadily increased. I’ve considered changing the food mix to include more phosphate and dialing back dosing but I haven’t gotten motivated to disrupt a stable system.

Adding phosphate is much much easier than reducing it. That’s a main takeaway from my current tank. It’s a different approach than I used previously.

All that said, i was worrying too much about phosphate when I started down this road and much of the effort was probably unnecessary. I did learn a lot.

Well, let’s hope I do not have to worry about it too much.

FWIW, I just upped my light schedule from 12 h per day to 15 h per day.

I also realize that I swapped out one of the 32 w led
bulbs and replaced it with a lower wattage when I used the 32 w for the anemone spotlight. I perhaps need to get another 32 w to replace it.

 

[rishma]

Well, let’s hope I do not have to worry about it too much.

FWIW, I just upped my light schedule from 12 h per day to 15 h per day.

I also realize that I swapped out one of the 32 w led
bulbs and replaced it with a lower wattage when I used the 32 w for the anemone spotlight. I perhaps need to get another 32 w to replace it.

I’ve never run a light cycle that long.

 

[TeeJay87]

It all depends on where you start this thought experiment, and what is being compared to what.

You assume there is already phosphate bound and it is going to come off. In that scenario, I certainly agree with you. A water change will not reduce phosphate as much as nitrate due to the desorption replacing some of what was lost.

But if you consider the entire process which must include how that phosphate got onto the rock, then I do not agree. Yes, the water change will still be exporting less than the 100:1 starting point, but the level in the water remaining will not be higher P than the 100:1 starting point.

. For example, when you put that starting 100 ppm. Nitrate and 1 ppm phosphate water into contact with rock, the phosphate level declines and you no longer have that same starting level. So even though the water cha ge removes less, it’s not enough less to overcome the initial drop.

Let’s try a different approach. You said the phosphate rises with each iteration. Forever? Where would it come from? There is limited phosphate on the rock. You can’t just assume it keeps coming off without accounting for it getting into the rock in the first place.

Ok, the different approach. What I mean by iteration is that you add another set of nutrients (100ppm nitrate and 1 ppm phosphate) and do another 50% water change. After NO3/PO4 input, the system NO3:PO4 is now 150:1.8 (1.8 because we ended last iteration with 0.4 in the water and 0.4 in the rocks per your example where half PO4 resides in the rock and the other half in the water). So now the 1.8 PO4 is 0.9 in the rocks and 0.9 in the water. We do another 50% water change. NO3:PO4 is 75:0.45 before leaching. And if we assume similar leeching, our ratio in the water at the end of this iteration is now around 75:0.68, which is climbing PO4 in comparison to the 50:0.40 ratio at the end of the last iteration. And the net NO3/PO4 input for this cycle is 25:0.28. So more PO4 than NO3 was added to the water column in round 2 in comparison to the input ratio.

 

[IceNein]

I’ve never run a light cycle that long.

For a refugium? Some people run a 100% photoperiod.

 

[rishma]

For a refugium? Some people run a 100% photoperiod.

Oh, I didn’t read carefully. You are right. I was thinking it was his display. Though I have not run a refugium light for 24hrs a day. I have run it >12 for sure

 

[BCash74]

Randy, wondering if you could guide me on something....

When I first got into reefing, the best piece of advice I got was to find someone who has a successful set-up and copy them. Then, once you have a successful set-up, then and only then incorporate/deviate/etc.....

I've been following this thread because I plan on copying a lot of what you've done; hoping it gives me the success I didn't have last time I had a tank... You convinced me to overcome my concern of hitchhikers and get the TBS sand and rock - thank you! I got my first shipment Friday and am thrilled with the rock! I'm also going to stock with copepods and amphipods and daily feed phytoplankton- something I've never done before. I also plan on growing ulva in my sump (never done that either)- I love how it functions not only is nutrient export but also as food for your yellow tang when you go away for a few days. And most importantly, I'm installing GCFI outlets. So, thanks for tips!!!

My question is on setting up a skimmer early on.... At some point I planned on adding a skimmer (maybe in 6 months or a year) when I needed greater nutrient export to keep things in check. However, would you recommend a skimmer early on for gas exchange and its contributions to pH regulation early in the process?

Finally, I'm new to this forum and don't do other forms of social media.... if I'm "hijacking a thread" or should be posting this elsewhere, please let me know (I won't take it personally :))

 

[Randy Holmes-Farley]

Ok, the different approach. What I mean by iteration is that you add another set of nutrients (100ppm nitrate and 1 ppm phosphate) and do another 50% water change. After NO3/PO4 input, the system NO3:PO4 is now 150:1.8 (1.8 because we ended last iteration with 0.4 in the water and 0.4 in the rocks per your example where half PO4 resides in the rock and the other half in the water). So now the 1.8 PO4 is 0.9 in the rocks and 0.9 in the water. We do another 50% water change. NO3:PO4 is 75:0.45 before leaching. And if we assume similar leeching, our ratio in the water at the end of this iteration is now around 75:0.68, which is climbing PO4 in comparison to the 50:0.40 ratio at the end of the last iteration. And the net NO3/PO4 input for this cycle is 25:0.28. So more PO4 than NO3 was added to the water column in round 2 in comparison to the input ratio.

I have a whole excel model set up to show data below over 12 months, but let's work through yours first for a couple of iterations, but accounting for binding and UNBINDING each time. Assume binding is always half of the amount IN THE WATER. I think this may clarify our different thoughts.

Start 100 nitrate and 1 phosphate
N: P ratio before anything happens is 100:1

Bind half of P --> 100 nitrate and 0.5 phosphate [now 0.5 P on rocks]
water change --> 50 nitrate and 0.25 phosphate [now 0.5 P on rocks]
water change removed 50 nitrate and 0.25 phosphate [now 0.5 P on rocks]
After Unbinding --> 50 nitrate and 0.25 P (already in water) + released P
.....we need to calculate the released P
total P now = 0.5 on rocks and 0.25 in the water = 0.75
half of that will be bound to rocks in new equilibrium = 0.375 on rocks
half of that p total will be in the water = 0.375 in the water
At end of full cycle in water: 50 nitrate and 0.375 P
N:P ratio remaining in water after 1 full cycle: 50:0.375 = 133:1
N:P ratio in water change water is 50:0.25 =200:1

now second iteration

Add 100 N and 1 P --> 150 N and 1.375 P in water and 0.375 on rocks [P total = 1.75]
Bind half of that new P total: 1.75/2 = 0.875 on rocks and 0.875 in water
Total in water after binding: 150 N + 0.875 P
water change --> 75 nitrate and 0.4375 phosphate
water change removed 75 nitrate and 0.4375 phosphate
After Unbinding --> 75 nitrate and 0.4375 P (already in water) + released P
.....we need to calculate the released P
total P now = 0.875 on rocks and 0.4375 in the water = 1.31 P
half of that will be bound to rocks in new equilibrium = 0.656 on rocks
half of that p total will be in the water = 0.656 in the water
At end of full cycle in water: 75 nitrate and 0.656 P
N:P ratio remaining in water: 75:0.656 = 114:1
N:P ratio in water change water is 75:0.4375 = 171:1

[edit: typo above corrected, and changed in the conclusion]
Thus, assuming I did the math correctly, the proportion of phosphate in the water change water is rising with each iteration (200:1 --> 171:1), and the proportion of phosphate remaining the the tank water is rising with each iteration (133:1 --> 114:1).


Happy to discuss further, and certainly to correct any mistakes I may have made. :)

 

[Randy Holmes-Farley]

Finally, I'm new to this forum and don't do other forms of social media.... if I'm "hijacking a thread" or should be posting this elsewhere, please let me know (I won't take it personally :))

Welcome to reef2Reef!

This is a perfect post and set of comments and questions. :)

Kind of puts the pressure on me. lol

I don't see a reason to delay on the skimmer unless its done for cost/spreading out expensses, which is reasonable.

The water will begin to collect organics and begin to yellow immediately after cycle, and will accelerate after you add foods. Skimmers also help aeration significantly, at least in my old and new tanks. I don't think it will be a driving force for nutrients too low, but if it is, feeding more or dosing N and/or P is, IMO, a better plan than not skimming.

Good luck!

 

[TeeJay87]

I have a whole excel model set up to show data below over 12 months, but let's work through yours first for a couple of iterations, but accounting for binding and UNBINDING each time. Assume binding is always half of the amount IN THE WATER. I think this may clarify our different thoughts.

Start 100 nitrate and 1 phosphate
N: P ratio before anything happens is 100:1

Bind half of P --> 100 nitrate and 0.5 phosphate [now 0.5 P on rocks]
water change --> 50 nitrate and 0.25 phosphate [now 0.5 P on rocks]
water change removed 50 nitrate and 0.25 phosphate [now 0.5 P on rocks]
After Unbinding --> 50 nitrate and 0.25 P (already in water) + released P
.....we need to calculate the released P
total P now = 0.5 on rocks and 0.25 in the water = 0.75
half of that will be bound to rocks in new equilibrium = 0.375 on rocks
half of that p total will be in the water = 0.375 in the water
At end of full cycle in water: 50 nitrate and 0.375 P
N:P ratio remaining in water after 1 full cycle: 50:0.375 = 133:1
N:P ratio in water change water is 50:0.25 =200:1

now second iteration

Add 100 N and 1 P --> 150 N and 1.375 P in water and 0.375 on rocks [P total = 1.75]
Bind half of that new P total: 1.75/2 = 0.875 on rocks and 0.875 in water
Total in water after binding: 150 N + 0.875 P
water change --> 75 nitrate and 0.4375 phosphate
water change removed 75 nitrate and 0.4375 phosphate
After Unbinding --> 75 nitrate and 0.4375 P (already in water) + released P
.....we need to calculate the released P
total P now = 0.875 on rocks and 0.4375 in the water = 1.31 P
half of that will be bound to rocks in new equilibrium = 0.656 on rocks
half of that p total will be in the water = 0.656 in the water
At end of full cycle in water: 150 nitrate and 0.656 P
N:P ratio remaining in water: 150:0.656 = 228:1
N:P ratio in water change water is 75:0.4375 = 171:1

Thus, assuming I did the math correctly, the proportion of phosphate in the water change water is rising with each iteration (200:1 --> 171:1), and the proportion of phosphate remaining the the tank water is falling with each iteration (133:1 --> 228:1).


Happy to discuss further, and certainly to correct any mistakes I may have made. :)

Yes - all good math here, but there is a mistake at the end. You have:

“At end of full cycle in water: 150 nitrate and 0.656 P
N:P ratio remaining in water: 150:0.656 = 228:1”

This should be 75 nitrate instead of 150 for both lines, which will change the second conclusion to “…the proportion of phosphate remaining in the tank water is [rising] with each iteration [(133:1 —> 114:1)].”

 

[Randy Holmes-Farley]

Oh, I didn’t read carefully. You are right. I was thinking it was his display. Though I have not run a refugium light for 24hrs a day. I have run it >12 for sure

This is my current display light schedule for all except the spotlight. I shortened it a bit for winter because the tank was too bright in the living room when it got full dark outside at 5 pm. I’m going to be slowly lengthening it a bit as spring progresses.

 

[Randy Holmes-Farley]

Yes - all good math here, but there is a mistake at the end. You have:

“At end of full cycle in water: 150 nitrate and 0.656 P
N:P ratio remaining in water: 150:0.656 = 228:1”

This should be 75 nitrate instead of 150 for both lines, which will change the second conclusion to “…the proportion of phosphate remaining in the tank water is [rising] with each iteration [(133:1 —> 114:1)].”

Yes, you are right. Thanks. :)

The effect is complicated, but it is true that phosphate rises relative to nitrate in both the water change water and in the tank water. I was wrong about the ratio falling in the tank. It's a curious effect where it rises in both places: tank water and water change water.

I think a simple way to think of this is that at the start, a lot of binding happens since the rock started empty. Over a few iterations the rock and sand are not taking up as much new phosphate, and so the tank water P rises. As it rises, water changes become a bit more effective at removing P (so more P in water change water), but that increase is not fast enough to offset the release from the rock (hence the tank water rises too).

Eventually, a steady state is reached where both N and P are stable (that is, end up at the same level after each iteration), and we reach an equilibrium in both N and P where the amount removed by water changes balances the inputs.

 

[TeeJay87]

Yes, you are right. Thanks. :)

The effect is complicated, but it is true that phosphate rises relative to nitrate in both the water change water and in the tank water. I was wrong about the ratio falling in the tank. It's a curious effect where it rises in both places: tank water and water change water.

I think a simple way to think of this is that at the start, a lot of binding happens since the rock started empty. Over a few iterations the rock and sand are not taking up as much new phosphate, and so the tank water P rises. As it rises, water changes become a bit more effective at removing P (so more P in water change water), but that increase is not fast enough to offset the release from the rock (hence the tank water rises too).

Eventually, a steady state is reached where both N and P are stable (that is, end up at the same level after each iteration), and we reach an equilibrium in both N and P where the amount removed by water changes balances the inputs.

You’re welcome; and thank you for going through the examples with me! It’s one thing to feel confident in the concept, but it’s another to communicate it effectively. And I could use some improvement in the latter for sure.

You make a valid point about reaching a steady state input output balance. I appreciate the discussion.

 

[Randy Holmes-Farley]

Elegance Update

In the last month or two, the elegance has really taken off. Not sure what, if anything, has changed, but it is now about 8” across, making it second only to the magnifica in size in the tank. :)

 

[dwest]

Elegance Update

In the last month of two, the elegance has really taken off. Nit sure what, if anything has changed, but it is now about 8” across, making it second only to the magnifica in size in the tank. :)

Awesome!

 

[Randy Holmes-Farley]

Magnifica Update

OMG, I thought I had the anemone issue beat with the higher light, but this morning I see that during the night it released from the island and is at the bottom of the back overflow wall. I assume it’s going to climb the overflow and fortunately I have not removed the powerhead guards.

Very frustrating. Maybe the light was too high, or maybe the issue is entirely unrelated to light. If I do move it back, I’ll reduce the spotlight intensity or time.

Just observing for now. Will be interesting to see how it changes color in lower light.

 

[X-37B]

Well, let’s hope I do not have to worry about it too much.

FWIW, I just upped my light schedule from 12 h per day to 15 h per day.

I also realize that I swapped out one of the 32 w led
bulbs and replaced it with a lower wattage when I used the 32 w for the anemone spotlight. I perhaps need to get another 32 w to replace it.

I have never ran longer than 12hr light cycles. Whats the reasoning behind the extended light cycle and what do expect from it?

 

[Randy Holmes-Farley]

I have never ran longer than 12hr light cycles. Whats the reasoning behind the extended light cycle and what do expect from it?

I don’t have a main tank light cycle longer than 12 h.

Do you mean my refugium?

 

[X-37B]

I don’t have a main tank light cycle longer than 12 h.

Do you mean my refugium?

Yea I thought it was the main display. Thanks

 

[Randy Holmes-Farley]

Overall Update

All creatures are doing well. Pictures in the next post.

The bubblegum digitata has grown enough from the little frag that it now sometimes serves as a hiding place for a damsel or chromis within its branches. That's a nice transition to see.

The clown trio seems well established and all of them love the anemone and get along well. I am totally pleased with this situation. One is clearly getting bigger than the other two, with one in the middle in size, as anticipated. As I have mentioned before, they never leave the anemone by more than 2", even if it is upside down on the sand. Once, after cleaning the glass after a lengthy time away, they all came out together toward the glass. I think they were defending the anemone against their own reflections. After a few minutes they seemed to wise up and stop doing so.

The male mandarin continues to grow and thrive. As the weather warms I am probably going to look into getting a mate. It will probably be a wild female since they are larger and more likely to survive in a tank where two small tank raised ones disappeared, perhaps into the claws of the mantis shrimp or gorilla crab.

Cyano continues to be an issue. Not sure what to do about that. It is partly gone in the AM, but expands during the day. I have used a turkey baster to remove it a few times and have added bacteria a few times afterwards to try to displace it, but that effect does not last long.

Yesterday morning, the magnifica ended up in a dark corner and was not attached well. That seemed a poor spot, so I once again placed it back on the island, where it is gripping on in good flow. I maxed out the Tunze powerhead that pulses water just above it, so it is not hit directly but gets turbulence when the powerhead pulses against the flow from the other end of the tank. I reduced the LED spot light from 32 w to 10 w, in case the 1000+ par was too much. I've not measure the new par, but expect it is in the 500 range (its about 300 with no spot light).

Curious issue while I was last away. I forget that the spot light was not going to change for daylight savings time, being on a simple electronic timer, but the AI blade lights did. Thus, when checking on the tank via web cam a half hour before total dark, the spot light as still on while the AI blades had dimmed considerably (2 h ramp down). I first thought the timer was stuck on, and that would have been an issue if it was on 24/7, but it shortly turned off and I remembered the daylight time change (something I strongly wish would be discarded).

Happy Reefing!