Trouble getting my Nitrate level down?

Question

I have a 55 gallon fresh water community tank that's been up and running for several years. I'm having a difficult time getting my Nitrate level down to 40 ppm and below.
I've been doing good with my weekly water changes of at least 35%. I also use a gravel siphon and clean accordingly when removing water. Fish are fed once a day with careful attention not to over-feed. Additionally, water is checked once a week and all Ammonia, PH and Nitrite levels are within compliance of my test kits recommendations.
Last year, I upgraded my canister filter to a Magnum 350 with dual bio-wheels. Fish store suggested getting rid of both of my power heads that I used to run my under-gravel filter.
Long story short, I have the Magnum 350 in addition to one power head running my (single plate) under-gravel filter.
Additionally, I also check my tap water for Nitrate and the readings are consistently 0ppm. Also using Diamond-blend in my Magnum 350.

How can I get the Nitrate down? Thanks!

Answer 1

Without knowing more about the fish load in the tank I would say you have done just about everything you can. A few minor suggestions though.



Dig a hole in your gravel over the undergravel plate away from the stand pipe and reverse the flow to blow what you can out of the space under the plate.



Also adding a few floating plants can be great to lower nitrates. Riccia and water lettuce are particularly good for using lots of nitrates out of the water.



Also 40ppm isn't a disaster or anything. Honestly I wouldn't be worried about that nitrate level.



MM

Answer 2

You've covered all the bases except the under gravel, when was the last time you reversed the crud out from under the plate, that maybe your problem seen as its only become a problem since you turned off the power head?

How long has the Magnum being run?

It could still take awhile for it to pick up the slack.

Is the Magnum run with the existing plate or separate?

If separate you could try running it on the plate as a purely mechanical filter, if that's what your doing then take it off as its being overwhelmed and put the powerhead back on for the moment.

I'd stop cleaning the gravel for awhile as that's probably your best source of beneficial bacteria. Keep doing the water changes and I'd increase the frequency.

Answer 3

The Nitrates are coming from your Bio-Wheels and undergravel filter. In Reef tanks, after the Aerobic bacteria is established to control the Nitrite and Ammonia, we ditch all biowheels and Bioballs. They are Nitrate breeding grounds. Basically your Bacterial cultures are outgrowing your tank.



And Water Changes will likely add alot of Nitrate. Tap Water will increase your nitrates by feeding ammonia to your bacteria. You could reduce your water changes to 20 or 25% every 2 or 3 weeks. That would be lots.



A 40ppm reading is pretty normal for an established tank.

Live plants will consume Nitrates and no, exces food and debris in your gravel won't be increasing your readings.

Answer 4

The quickest answers is probably to add live plants in. Live plants absorb nutrients from nitrates. Nitrates are the better type of chemical than ammonia and nitrite. I wouldn't worry too much about these guys.

Answer 5

You must have some uneaten food in that tank somewhere - I used a gravel syphon too, and it dod a great job - but there are always places where food can end up uneaten. Just how big is your tank compared to number of fish? I would say as a couple of suggestions:

Buy a scavenging catfish

Feed less often.