• Looking to buy a cephalopod? Check out Tomh's Cephs Forum, and this post in particular shares important info about our policies as it relates to responsible ceph-keeping.



Sep 2, 2006
Hey there,
I have a 65 gal tank that has been up and running for about 4 months now. It will eventually be for an octo once everything becomes mature and stable. It cycled in about 2 weeks, but for the past 2-3 weeks my nitrates have been thru the roof - around 80ppm. My ammonia & nitrites are at 0, PH at 8.2, temp a constant 77 deg. I've done 15-20 gal water changes every week but it doesn't seem to be helping at all. My source h2o is RO/DO. I also have a 15 gal sump, 70 lb live rock, 2 in sand bed, and current inhabitants include: 20+- blue legs, 10-15 snails, 3 tiny urchins, small xenia, 1 polyp duncan coral, and 5 tiny mushrooms. I'm not feeding anything other than the occasional piece of shrimp to the duncan - and hermits get leftovers (if there is any) Everything in the tank appears to be doing fine, but I know it could take a while for corals to show distress signs....
Any ideas on what could be causing this nitrate spike - and more importantly how to get it down, and stay down?
Thanks for any thoughts!
(PS - I've tested with 2 different tests, both came out the same)
Sounds like you're doing a pretty good job on what you've got going. Xenia is pretty intolerant of problematic water conditions, and would likely show you some major distress very quickly. Like fine one day and melting the next. The duncans on the other hand are pretty tough. Using a second test kit is what I would have suggested but you've already done that.

I would suggest holding off on feeding the tank so you're not adding to the issue. Keep up your water changes as you're doing. Most of all, just be patient. Judging by your post I think you're already doing everything right for the most part.

Do you have a skimmer in your sump or on your tank? Are you keeping any macro algae in your sump?
I do have a skimmer in the sump, but it's only rated for a 40 gal (from an old tank). It was out of commission for about 2 days, but I don't know if that would cause this much of a spike. I have a new one coming tomorrow - rated for a 175, so it shouldn't have ANY trouble with a 65! I also plan on getting a few mangroves for the sump as well, but that will be another week or 2.
The only thing I have found to reduce nitrates (or at least hold them steady) is to regularly vacuum the substrate. There is a relatively new hand siphon out that has a decent diameter tube that I have found useful during water changes (I found mine on eBay but Petsmart had them cheaper - about $4.00 - The on-line version is twice that - http://www.petsmart.com/product/index.jsp?productId=2755281 ). It does a reasonable job of letting you run it through the sand and suck up the cloud of waste (even better if you turn off your pumps). On the expensive end, Eheim makes a sludge extractor (Aquarium & Fish Tank Gravel Vacuums | PetSmart) that is also useful if you want to clean more that the amount of water you are taking out (or in my case have a 3 foot deep tank to clean). It does not seal very well and is expensive to fix. I suggest NEVER submerging it without a water tight cover over the handle (a Trojan prophylactic works well :sly:).

Reducing your sand bed might help too. From what I have read, if you are not going to have at least 6 inches of sand, there is no biologic benefit from a sand bed. When I reduced my sand layer in my 15 gallon, it helped a lot keeping the nitrates in check (in addition to the above mentioned weekly cleaning routine).

Shop Amazon

Shop Amazon
Shop Amazon; support TONMO!
Shop Amazon
We are a participant in the Amazon Services LLC Associates Program, an affiliate program designed to provide a means for us to earn fees by linking to Amazon and affiliated sites.