Nitrate issues in Red Sea 525xl 139 gallon tank

[Kevin1214]

I currently have a 9 month old mixed reef tank. I have been battling high nitrates for the majority of this tanks life and I was wondering what I can do to combat it. Currently I have a solid amount of corals and around 14-16 fish ranging from small to large. below are my parameters and nitrate reading based of a API spin test would love to know what could be the issue bringing all these nitrates could it be the bio load. The sand and the rockworks were reused from a tank before this one that was a year old As well. I feed two cubes of frozen Mysis shrimps and 1-2 nori sheets every other day. water change schedule is not set 100% sometimes once every two weeks or once every month depends on time. But still once I do a water change it will drop a little and then spike right back up in a day or two would love some help on this issue. I recently added a marine Bio block and seeded it with microbacter 7 for 12 hours placed it in a low flow area but still nothing.

Parameters as of today Parameter 7/16/2024

ALK-167 PPM ALK 179
PH 7.9 PH 8.0
PHOS 0.1 PHOS 0.1
CA 469 CA 451
MG 1392 MG 1497
AMMO 0.0 AMMONIA 0.0
NITRITE 0.1 NITRITE 0.2
NITRATE 63 NITRATE 25

 

[kvansloo]

How old is the sand and rocks.

 

[Kevin1214]

Sand and rock is mixed some 9 months old and some from an older tank so about 2 years old

 

[kvansloo]

How often do you do water changes?
What was Nitrates in old tank? Did this issue move from the old tank?
I would not have reused the sand at all, and I would have at least rinsed the rocks with saltwater to remove debris. But that is me. Have you tried doing a 50% water change then test nitrates 24 hours later too see if they go down.

 

[Kevin1214]

The older tank the nitrates would be around 5-10 ppm. I have never done a 50% but I have done a 40% when nitrates where around 50ppm it dropped it down to 25 ppm nitrates but then again after 2-3 days right back up to 50. I did sadly reuse the sand as I didn't know it was a bad thing back then now I do know the rocks were cleaned when I removed then and put them into the new tank.

 

[kvansloo]

Yeah, I never reuse sand but some people do. I have had my 90 gallon for 15 years it has a 3.5 inch sand bed. I have to replace the sand every 4-5 years do to nitrates going up over 65. ppm. when mine starts going up and water changes don't work any longer I remove the rocks to tubs with saltwater and shake them to remove debris, put inhabitants in another tank and remove and replace the sand then do a big water change and put things back nitrates usually go down to .5 - .10 ppm. I am about to do it again and I will not use as much sand this time around I will have 1- 1.5 inch sand bed also when doing water changes do you vacuum the sand some detritus could be in/under the sand

 

[kvansloo]

You can also rinse the sand, and try that but I have not had any luck doing that. I just buy new sand and rinse the heck out of it. then put it in the tank.

 

[Lavey29]

I would suggest you dose PNS probio which is a natural heterotrophic bacteria that eliminates organic waste before it becomes nitrates. I dose it once a week. My nitrates stay around 15 consistently.

You can also wet skim more but there is nothing wrong with elevated nitrates unless you see tank issues from it.