Constant Nitrate Problem

[WannaRace]

Before anyone tells me that this project is just simply not going to work, I would like to exhaust all options and paths to success.

With that said, I started a 6 gallon fish-only tank a little more than a month ago. In the display I have 6 lbs. live rock, sand, powerhead, and a HOB filter that has two compartments which water flows through. In the first compartment, I have live rock rubble only. Then the water flows to the second chamber which houses some denitrifying rocks (basically very porous rocks that absorb ammonia, nitrite, and nitrate). Finally, it flows back into the tank.

The problem is, I have never seen nitrates drop below 20. I do a 17% water change once a week. Before I change the water I test for nitrates and see that during a weeks time they jump to 40-60. All other parameters are spot on, perfect.

Any ideas as to why this dramatic increase occurs? I realize that in such a small tank huge changes easily happen, however, why isn't going from, let's say, 0 to 20 in a weeks time rather than 20 to 40 or 60. Any suggestions?

[RyanG]

Are your useing RO water? It may still be cycling too.

[reeffreak]

Keeping nitrates at zero in a 6 gallon tank is a daunting task.There just isn't enough water volume to work with.Maybe increase water change to double the amount and reduce feeding-bioload.

[WannaRace]

I am using distilled for water changes, but tap with a liquid dechlorinator for top-off. I tested the tap water for nitrates and saw 0ppm. Anyway, I am switching to RO for top offs to see if that helps any. I wonder if, although ammonia and nitrites are at 0, the tank is still cycling...

I will try doubling the amount in water changes, however, I have added no livestock to the tank. Until I see stable water parameters I do not plan on adding anything. I can play with my 30 gallon while I wait

[WannaRace]

Today I am looking to siphon out all of the brown, what looks to be die-off from the rocks. Is it advisable to take the rocks out and shake them in saltwater to remove everything? It would make siphoning out everything off the sandbed a lot easier. Then I plan on doing a water change, leaving the top open, and testing for nitrates again.

[yote]

Try using a powerhead and blowing that stuff off the rock.Then siphon it out.Thats a lot easier than scrubbing each rock in a bucket.

[reeffreak]

No problem taking the rocks out and giving a good rinsing in fresh saltwater.I would go as far as scrubbing the dead stuff off with a old toothbrush.I believe the cycle is over but the decaying matter is raising the nitrates.If you're going to use tapwater,Prime is a better dechlorinator,it detoxify ammonia,nitrite and nitrates on top of heavy metal and chlorine.

[Bifferwine]

I agree with both Yote and Freak, you can either blow off the crap with a powerhead or turkey baster and catch it in a net, or you can scrub the rocks one by one with a toothbrush.

[Alexander]

just let it wait a bit for the cycle to really come to a rest before you get too discouraged. i would use a brush and get all the stuff off the rocks in a seperate container just so it lessens the chances of more crap staying in there. you may not be able to suck it all out if you kick it up all over the tank

[WannaRace]

Thanks guys..I really think that the nitrates were never getting lower than 20 because I was only changing the water, when in fact, there was a LOT of die off and other crap within the rocks and on the sandbed. I blew it off with a turkey baster, siphoned most of what I could from the sandbed, and while I still had debris floating around I did a huge water change. I guess I will continue to do this until I can reach some stable water parameters.