Some SPS tips are not active & slowly dying

[Ace Park]

Wish you a prosperous new year!

I have a cubic nano tank with small sump as following configuration :

18 inch cubic tank with 12 inch cubic sump
Radion G1
Salinity : 1.027
Hardness : dKH 8
Salt : Redsea coral pro
nitrate : 0 ppm
phosphate : 0.25 ppm
Mg : 1500 ppm
Ca : 520 ppm
Water change : 5 gal / week

Most of SPS's polyps are not widely expended except pocillopora. Green pocillopora looks very healthy and has been growing well.

Another specie that is very rapidly growing and healthy one is ORA pink Digitata. A few of montipora seem good as well as incredible growth.

Only except above cases, most of SPS's tips are not active and have turned brown, died at the end.

* summary
1. Many montipora except starburst cap are very healthy
2. Most of SPS' are not healthy with short polyps even died out except green pocillopora

Mg and Ca values are pretty high but I believe these figures are not that critical in terms of SPS health. However I am controlling it very slowly.

Any opinion in regards to this matter would be appreciated.

 

[dubmaneh]

I don't have experience with the Red Sea salt but salinity calcium and alkalinity seem a tad high. Especially given zero nitrates.

I would lower salinity to 1.025-1.026, let calcium and alkalinity fall to around 450ppm and 7.5dkh Also feed more to get nitrates to 2.5ppm.


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[Ace Park]

Thank you dubmaneh!

I am also a little bit curious about the Ca and Mg level. I will try to decrease them slowly.

 

[miralami]

Assuming your phosphate measurement is correct, it's way too high.
Start dosing KNO3 to balance.


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[Ace Park]

Hi Miralami,

I tested phosphate level by Selifert and it was hard to measure. Need to find better way to check. Thanks!

 

[outssider]

Hi Miralami,

I tested phosphate level by Selifert and it was hard to measure. Need to find better way to check. Thanks!

If you want to get real accurate phosphate measurements in the low range use this.....Hanna Checker HI-736.....it reads in ppb phosphorus that is easily converted to ppm phosphate

 

[reefmutt]

I don't have experience with the Red Sea salt but salinity calcium and alkalinity seem a tad high. Especially given zero nitrates.

I would lower salinity to 1.025-1.026, let calcium and alkalinity fall to around 450ppm and 7.5dkh Also feed more to get nitrates to 2.5ppm.


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Assuming your phosphate measurement is correct, it's way too high.
Start dosing KNO3 to balance.


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I would agree your troubles are due to these issues..
If dosing kno3 is not something you are comfortable with, adding a few more fish and gently using (but ramp up) some phophate removers would also help.

 

[Ace Park]

Thank you very much. I will try that way.

 

[NeverlosT]

the issues I see here are salinity a bit high and calcium a bit high.

I have seen plenty of successful SPS tanks with phosphate higher than that, not to say your tank wouldnt benefit from lower phosphate, Im just saying be careful latching onto that as the red flag.

 

[reefmutt]

the issues I see here are salinity a bit high and calcium a bit high.

I have seen plenty of successful SPS tanks with phosphate higher than that, not to say your tank wouldnt benefit from lower phosphate, Im just saying be careful latching onto that as the red flag.

Are you sure you've really seen successful sps tanks with p at .2 AND n at 0?
Yes with n elevated as well, but with n at 0 and p so elevated, there is a serious imbalance here.

 

[NeverlosT]

Agreed, I think n at 0 is a problem with high P. I was just suggesting not to focus just on the phosphate. I think the range of phosphate levels that can result is rather large.

 

[dkeller_nc]

You mentioned changing 5 gallons of water in this tank every week. Just doing a rough calculation, I'm going to guess that your actual system volume is around 20 gallons (accounting for the volume taken up by rock, pumps, etc...).

Red Sea Coral Pro, when mixed accurately, is going to have an alkalinity of about 12 dKH. If your tank is kept at a dKH of 8.0, then that 5 gallon water change will result in an alkalinity rise to 9.0 in an instant. And if you're not dosing to maintain the alkalinity at 8.0, it's pretty likely that your alkalinity was a good bit lower than that at the water change, so the swing was even greater.

This kind of alkalinity swing is extremely detrimental to acropora species, and might explain why your other corals (pocillopora/montipora) are doing well, but the acropora are not.