So I've had my 14 gallon biocube setup for just under a year now. My first venture into the realm of saltwater.

My setup includes:
Stock everything except:
Maxi 900 pump upgrade
Hydor flow
100 watt heater

Stocked with:
About 12 pounds of LR
About 2 inches of live sand
various hermit crabs/snails
1 Ocellaris Clownfish
1 6 Line Wrasse
1 Cleaner Shrimp
1 Peppermint Shrimp
Green Star Polyps
Green Mushroom
Nepthea

I use distilled water for PWC and top offs

Everything has gone great, no problems at all/ aside from an on going aptasia battle. All fish/inverts are healthy. Lots of pretty red coralline algae covering the rock/walls. The coral I just started adding about a month ago and I've seen significant growth (especially on the green star polyps and Nepthea). I did things very slowly and that seems to have worked out.

My question is on Nitrates. Within the first couple of months, Nitrates would build up to about 10 or 20 before a water change. After about 3 months I they were always zero when tested, but I continued to do pwc. I found this a little suspicious. As a keeper of freshwater fish (including messy goldfish) nitrates have always been something that has to be kept in check with water changes. I decided to stop doing water changes on the biocube to see if they would eventually build up in the water, but my test kit STILL reads zero after months of just topping off. I'm using an API master saltwater test kit, and I even borrowed a friends to see if maybe my kit was old. Still zero. Since adding the coral, I've started on the PWC again, albeit pretty infrequently.

What the heck is going on here? Where the heck is all the waste going? I don't have a nitrate sponge or anything like that. Is it necessary to do water changes if you're Nitrates are zero? (not that I mind). I'd like to get a handle on this before I add any more coral.

Any help would be appreciated.

are you using any media that would remove Nitrates? Is there algae present eating your nitrates makign them undetectable?

those are my first 2 thoughts.

I just looked at my tank and it really only looks like the coralline algae with a few green patches on the rock mixed in.

The only media I have is what came with the tank: bio balls, the filter cartridge which I've changed like twice (usually just rinse it off in tank water), and the sponge by the pump.

Edit: Also a couple small bubble algae blobs that have been there from the start. They haven't spread.

Well you have an amazing clean tank with 0 nitrates. I am not sure how you are doing it either at this point but congratulations.. I just dont know what else to say.LOL

Is it necessary to do water changes if you're Nitrates are zero? Yes you do. Nitrates are not the only reason for water changes. You change water for mineral replacement as well. Without water changes your animals do not get the trace elements they need to thrive replaced. (coraline algae even requires trace elements to continue to thrive.) So even without nitrates I would still recommend 10% water change weekly for element replacement. (might want to get a test kit for calcium and the other trace elements that your coral and animals are using)

Congratulations and Happy reefing. (hopefully someone else can chime in with other ideas or somethign constructive as well.

One thing you might want to try is stop using distilled water for top offs and tank changes, instead use RO/DI water. I have read that distilled water has no trace elements or other nutrients. Distilled water should be completely sterile.

I'm also having this problem? If you can call it that... Also, my Phosphate level is always at zero. I am using Denitrate in a canister filter. One problem I'm having is I'm not getting any growth on my LPS, though they look healthy.
This is my set-up.
24gal Aqua Pad
25lbs of live rock

Magnesium = 1230
PH = 8.2
KH/Alk 8.6
Calcium = 510
Phosphate = 0 ? Not sure why is always 0
Nitrate = 0? Same thing as Phosphate not sure why

Corals: Pipe Organ, Candy Cane, Green Toad Stool, Torch, Birds nest, Pom Pom Xenia, Zoanthids
Filtration: CPR Bak Pack skimmer and a canister filter with Denitrate and filter pads (fine and course)

Lighting: Nova Extreme Pro 6X18 watt 20 inch, three of the bulbs are 10k and the other 3 are 460nm Actinic.

two forces work in an established tank, algae, and denitrifiing bacteria, ok and some coral to some degree

algae uses the nitrate to grow, if you remove algae, you are removing nitrogen
the bacteria are anerobic and may live deep in rocks where no oxygen can reach, also in deep sandbeds. they convert the nitrates into nitrogen gas

it is said that some soft coral like xenia incorporate some amount of nitrates into growing, which makes sense for just about all photosynthetic corals since they all contain algae

I've also seen several tanks who only get water changes a few times a year to even once a year. Usually they have a very low bio-load and they aren't overfed. One of my friends has had his 29 gallon Biocube for 5 years and he only does water changes once a year. Granted he only has a pair of clowns and a dottyback, along with 7 RBTA's that keep splitting. A few polyps, but nothing fancy. He feeds his tank twice a week some flake food and leaves it alone.

The phosphates and nitrates are consumed by the bacteria in the LR and other than a pinch of food his tank has no other nutrient creaters. It's actually a perfect balance and mini ecosystem in a box. My problem is I overfeed because I love to watch my corals grow and multiply and I keep adding more.

Good point.

To clarify on this, there's a difference between zero nitrates and and nitrates being metabolized in the tank to the point they are non-detectable. The later is the far preferable.

If you have fish and or some being inverts like a CB shrimp, then you have nitrates, period. If you have a deep substrate made of sand, and a lot of established LR per fish ratio, then nitrates are being consumed.

Rapid corraline/xenia/zoa/shroom growth in my experience usually means nitrates are being consumed. My 10gal nano has no fish/inverts in it, and I have to add some nitrate from my freshwater tank. This has produced obvious growth with softer corals.

Agreed. I've noticed that tanks are very capable of processing far more than they are normally given credit for, especially more naturally modeled systems and those with substantial coral growth. A combination of all of the above is very desirable and represents very closely what would happen on the reefs (although reefs have many more means of nutrient export, almost all of it is bound in living organisms, including corals, algae, etc.).

Another example is when a tank is overrun by green hair algae. The tank will test with 0 phosphates and low nitrates, but it's because the algae is consuming the excess nutrients. Hence the reasons for refugiums that we grow macro algae in to consume the excess nutrients, if your bio-load is too high for the LR, filters, skimmers, etc to consume them. It's always interesting because we're always looking for a perfect balance, but for most of us we're always rebalancing because of the addiction. Adding more corals, fish, etc., and in essence always changing the chemistry of our water. Trying to find that perfect balance, but there are too many nice corals out there to stop:)

Same goes for me I've had zero nitrates and zero phosphates for ages. As funny as it sounds I do have 3 flame angels, 2 true percs, hermits, snails, 2 bumblebee shrimp, 2 pompon crabs, various corals hard and soft. Feed 2 times a day average, pour in 3-4 different times of plankton and most ployps are fed everyother day. Even with all that still not a hint of nitrates. Can't get algae to grow on my glass if I wanted to. But one can't forget that the type of filteration you have does make a big difference as well as the amount of flow.

well the nitrate spike are coming from your bioballs in the rear chamber if you are not cleaning them reguarlly they build up bacteria and waste so get rid of those to fix the problem or do regular cleaning

How does that work? In the same tank?

+1

I was thinking the same thing. How big is your tank and are they nipping your corals? I like the flame angels, but never wanted to risk them eating my corals

I have some you can have.

They're 50/50 for the coral x-factor.

Op: I think you must be maintaining your system very well to not have any nitrates!

He said he has NO nitrates.

OP... could you post a pic of this tank?