Nitrate too high

My tank finished cycling, it's been about 7-8 weeks. Here are my tank stats:

PH 7.9
Ammonia 0
Nitrite 0
Nitrate 20 ppm

I've been testing the tank every few days and the nitrates dont seem to be coming down. I had 0 nitrite at week 4. I'm also getting a lot of brown algae/diatoms growing all over my rock and tank walls.

Here's my setup:
112G tank with 40G sump
I'm using a vertex IN 180 protein skimmer, 700 GPH return pump and 2 modded maxi jet power heads pushing 1200GPH each. Plenty of flow IMO. For lighting I'm just using some 6500K compact florescents in some shop light cans (temporary setup).

For substrate I'm using CaribSea Select grade reef sand. It's aragonite/oolitic. For rock, all I have is some DIY rock that I made out of oyster shell and portland cement. I cured it for 6 months in tap water. I use Instant ocean salt and a spectrapure RO/DI filter for my water.

I have 0 fish, 0 Invertabrates but my nitrates are still high? What is the problem and how do I fix it?

Thanks in advance, I can't figure this out.

 

You will need a way to export the nitrates, like using macro algae or doing some water changes, 20ppm isnt that high, and seeing how your tank just cycled I would say normal. Do some water changes or get some cheto in the sump and they will come down.

 

diatoms are normal part of cycle they eat all the silica leeched form new glass/plastic then die off usually within 3 months IME.

Nitrates in a new tank are primarily removed by the skimmer, water changes and any macro algae in sump/fuge. the bacteria that convert nitrates to nitrogen gas take a very long time to colonize the tank since they live in low oxygen environmnets (deep in rock, bottom of sand bed, etc).

 

Perfectly normal and fine for you to have some nitrates in your tank. Remember that even 40ppm is "ok" for fish only systems, and 20ppm is (borderline) acceptable in a reef tank. The more toxic compounds are ammonia and nitrite.
The only real way to keep nitrates at absolute zero is to have an effective refugium with lots of macros, some type of denitrator (coil/sulfur/etc) and use of nitrate absorbing animals, like bivalves.
Since you don't have livestock, get your pH up. Test your dkH and make sure your buffer is where it should be.

 

I agree with the other two posters. 20ppm isn't TOO high in the grand scheme of things, especially considering there's no livestock to be harmed. I would suggest 20% water changes or greater and time to allow your natural flora to develop.

I would assume your tank has not yet finished cycling. As a part of your nitrogen cycle (Ammonia > Nitrite > Nitrate), nitrate is the last to finish. I would venture to say you probably had ammonia and/or nitrite at week 4 when nitrates were 0. Having them now would suggest to me that the process is finishing.

I didn't see you mention the amount of live rock you have in the tank, this is most likely contributory to your problem if not adequate.

 

I disagree this is the "only real way". I have never used any of these 'requirements' and I maintain 0 nitrates.


I can say, once my ammonia and nitrates 0'd out and my nitrates dropped to 20 (like you) is when I said "cycle over". It took another couple months, but the nitrates dropped on their own.

As long as they're not climbing, in your situation, I would just monitor and give them time to come down on their own.

Adding livestock will hinder that from being quick though...


That's not to say tigermike's suggestion is bad or wrong. They are good and if your nitrates climb or don't drop after some time, would be good steps to take.

 

Thanks for the replies.

pgoodsell: Do you think I could add a fish? What would you recommend? I want a Blenny or Goby, or maybe a Royal Gramma. My nitrates IMO killed the turbo snails I tried to add at week 5. I don't want that to happen again.

rdarris: Thanks for the advice I appreciate it. I didn't know that nitrates get converted to nitrogen gas.

tigermike 74: How do you suggest I get my PH up? My test kit didn't include dkH, is there a kit you can recommend? What is my buffer?

DXJoe: I have about 60-80 lbs of my home made live rock. I'm planning on seeding it with 20-40 lbs of some good rock with corraline algae on it once I get my lighting upgraded. By week 4 I did detec a small amount of Nitrate but it was about 5 ppm.

Thanks for your replies again, K+ to all of you.

 

I don't think nitrates at 20 (or even 40) ppm would kill snails. I doubt that was the problem.

 

So do you think I should just ride it out for 8-12 more weeks before adding any livestock? Personally I don't want to unecessarily chance losing any livestock.
Thanks for the reply k+

 

I just have the API saltwater master test kit. Is there any test kit/ tests you would reccommend besides the basic ones to keep my snails from being murdered? Any ideas what might be the problem? Low PH maybe?