reviving a dormant tank - high nitrates


Reefing newb
I left my 20g tank go dormant with no live fish for about 6 months, kept the filters running (u/g and penguin 300 bio-wheel) but no lighting. I revived it 2 months ago with a 50% water change, new additional lighting and a new Eheim 2213 canister filter to replace the penguin. The filtration provides incredible water flow through the tank. After the 50% change the water had -0- ammonia -0- nitrite but 80-160 nitrate. I left it run 2 weeks without stocking. Added an anemone and small hard coral and banded shrimp - all of which have been doing fine over the past 2 months. Over that time I also added a small blue tang and a week later 2 small clowns, all of which died within 10 days. I have been making weekly 1g water changes and continue to have extremely high nitrates, all the while adding regular and generous portions of Instant Ocean Nitrate Remover, which has done nothing. I checked my tap water and it has nominal nitrates. Why don't the nitrates go down?
Chances are your rock and sand are releasing nitrates over time. You really should remove all animals in the tank, and not add anything until you improve your water quality.

The canister filter is not doing you any favors -- they can actually lead to higher nitrates over time. You should also switch to RODI water instead of tap water. 1 gallon water changes weekly are not enough to make a difference. If I were you, I'd be doing 30 to 40% water changes weekly (up to 8 gallons a week), until nitrates get down to an acceptable level (20 or below).

I'm confused as to why your inverts are still alive with your nitrates being that high. Be sure to buy a new nitrate test kit and test it again -- test kits go bad after about a year or so, and are unreliable and can give bad results once they expire. If they really are in the 80 to 160 range, then you definitely have to get all those animals out of there, I don't care how good you think they look, you are slowly poisoning them with that water. Nitrates that high is just uninhabitable for marine animals.

And I'd really strongly recommend that you not add any more tangs, especially blue tangs. They need tanks sizes much larger than yours -- at least 75 gallons. If the water quality didn't kill your fish, the small tank size was the culprit. Tangs need a lot of swimming space (at least 4 feet), and without that swimming space, they get stressed and die pretty easily.
Hello and welcome...I totally agree with Biff on everything she said. The only way to get rid of the nitrates is with water changes...and lots of them.
Also, an anemone need pristine, damn near perfect water, to survive and ultra bright lighting...that could also wiped the tank out too...good luck and keep us updated. :)
thanks for the fast responses. i figured the 50% change would be adequate and have done the 1g weekly as a maintenance, but will change more. the test kit is new. in the can filter i cut back the volume of the substrat (biological filter media) since i have the u/g and in its place i put in a chemi-pure bag which i used years ago with much success. i am stumped at the vibrance of the inverts too and think i am going to take a water sample to a store for a second opinion. i added more light and now have 2 actinics and 1 10,000k. i read good reviews of the instant ocean nitrate reducer but it hasn't done anything. would you continue to use it along with the water changes? what is rodi water?
Definitely take the water sample to a store for another opinion. Those nitrate reducers usually take a while to start working -- does it say on the package how long before you are expected to see results? If it's been in there for a while and nothing's changing, then you could stop using it.

RODI water is reverse osmosis de-ionized water. It's a method of purification. You can buy it at any Walmart or grocery store. You can also use distilled water. Those would be much better than tap water.

If all else fails, you can try adding this to your tank:

Marine SAT - Hair Algae Remover for Reef & Saltwater Aquariums 32 Oz.

It's an algae remover, but will reduce nitrates safely as well.

But before you do anything, get those parameters double checked at a fish store.
And just to add what Biff said, I'll also suggest getting rid of the underground filter. It contributes to high nitrates also.
I didn't even notice the undergravel filter. Good catch Smitty. That could definitely be causing nitrate problems. They are not good for saltwater tanks for that reason.