Nitrate issue, stumped!

[doomer71]

Hello everyone, new here to the forums and the hobby. I cant get nitrates below 40-60. Done a few 10 gal water changes, couple 20 gal changes over the last 5 weeks and even after a change it doesnt lower at all. My lfs guy is stumped as well.
History: bought this tank used, tossed the old live rock because it was covered in thick white stuff and seemed to be very old rock. Bought new tonga to replace it. New live sand 60lbs. Pre mixed water from lfs grav at .023. Cycled completely and everything was good.
New coralife 125 skimmer. New hydor controler and 2 850s. New orbit LEDs. Its 72g bowfront with 20g sump (sump also new before cycling). Have 20 various hermits, 20 snails, shrimp, tiger striped sea serp. 2 clowns, 2 flametails?, 1 condy 2 frags. Parameters were still good. A few weeks ago nitrates rose and wont go down. Nothing else has changed in the tank.
Tryed de-nitrate, no change. Skimate is nice and dark.
Feed dime size rods frozen daily (gone in about 1 min), condy gets hikari brine and the crabs and fish live it too every other day or 3rd day.
Phosphate .25
Nitrite 0
Amonia 0
Calcium 440
Kh 143
Ph 8.1
Grav .023
Nitrate 40-60 using api / 35 using red sea

Fish and condy seem happy and healthy.
Dont know what else to try, please help.

[MinnFish]

Welcome to RC. I do have a few questions. First, what size tank? How long has the tank been up? Why has the LFS, not inform you to bring the salinity up to .026? Happy reefing.

[acabgd]

Few 10g and couple 20g water changes over 5 weeks might not be enough. If you change 30% of water at once your nitrates should go down 30%, meaning 25g change will lower from 60ppm to 40ppm. If you have a nitrate source in a few days you'll be back at 50ppm and a week later again at 60ppm. With even smaller water changes you might not see any difference at all.

Did you try feeding way less?

[doomer71]

72g bowfront w 20gal sump as in the post

[sherief.elsayed]

Hey doomer71 I have a 90 gallon, what I noticed worked in my case was to try to monitor the feeding habits and feed a little less acabgd posted, this had helped me reduce it along with 20% weekly water changes. Make sure all your filter media is clean and filter socks changed every 3 days to a week. I'm semi new to the hobby 9 months, but I have found this to work for me. Eventually a pattern develops and you should be able to maintain it easier In the long run.

[zn00py]

i would do 50% water changes at least 2 in 6 days and test again. Rea Sea seems to be a better nitrate testing kit. API test kit for nitrates are not reliable

[doomer71]

I was worried a 50% would cause another cycle or crash it

[oakengineer]

Any possibility you can cultivate some macroalgae in you 20 gal sump?

[doomer71]

Yes I could try macroalgae, but more concerned what the problem is with such a low load of 4 1inch fish, 2 1" frags and small cleanup crew. Shouldnt be so high steadily should it? If so what happens when its stocked up more? Plan is for mixed reef tank in the long run.

[Dan_P]

I was worried a 50% would cause another cycle or crash it

The bacteria that make up your nitrification filter live on surfaces. A water change would not reduce their number.

If you are concerned about large one time water changes, do smaller daily changes. They are a bit less efficient (you will use somewhat more fresh brine to dilute the components of interest) and will take longer (only a problem if you must bring down a concentration of something rapidly).

If water changes are not making a measurable difference in nitrates, the test is bad or nitrate production is very high.

[Triggerfish]

http://reefcentral.com/forums/showthread.php?t=1977420