Can'y lower Nitrates!!!!!

[BanZI29]

I have been fighting high nitrates for about a month now. I upgraded my tank to a 40 Gal 2 months ago and had a mini-cycle. ammonia and nitrites are 0 but nitrates are stuck at 48 (Hanna tester) I did 2 50% water changes and that has had no effect. It looks like I have Dino's in my sand.( I think thats what it is) and its getting worse. ( I think thats what it is) and its getting worse.

Tthe LFS suggested this stuff from SeaChem:

What do you all think? is this good to use? is there anything else that I can do?? I also got 2 Diamond Gobies today so I hope they will clean up the sand.

Current Params:
Salinity = 1.026
Ph = 8.1
Ammon. = 0
Nitrite = 0
Nitrate = 48
Phos = .024
Calcium = 490
Mag = 1430

 

[TheBear78]

Double check your test results with a completely different kit. Two 50% water changes and no reduction in nitrates makes no sense. Chasing numbers by adding products can be a never ending cycle...
More fish will of course not help the nitrate issue but may help with the sand bed. It looks more like diatoms to me, what is your phosphate level?

 

[BanZI29]

Double check your test results with a completely different kit. Two 50% water changes and no reduction in nitrates makes no sense. Chasing numbers by adding products can be a never ending cycle...
More fish will of course not help the nitrate issue but may help with the sand bed. It looks more like diatoms to me, what is your phosphate level?

I tried a Nyos test too and it was the same. The nitrates did lower a bit after the water change BUT they went right back to where they were after a couple days.
Phos is .024