HOB Filter and Nitrite Spike

[Mrkrsll]

I took my HOB filter off my 20 gallon and the next day, nitrates dropped to about 5 to 10 ppm down from 40, nitrites went to zero and ammonia was already at zero...

A few days later, I moved some rocks around and there was a lot of debris floating so I put the Hob filter back in with some filter floss. Woke up this morning, check my water parameters and the ammonia is still at zero, but my nitrites have shot up. Nitrates are still around 5 ppm.

 

Why would the HOB filter and filter floss shoot nitrite levels up after less then 24 hours?

 

Currently there is no fish in the tank, but I do have a few snails and a couple small crabs. Not sure if these swings are going to hurt anything...

[Jellyingabout]

Ammonia was at zero but nitrite may have been high which was converted to nitrate overnight. It may be the tests you are using, many tests aren't that accurate so your zero reading may be close to your 5 reading and really your nitrates haven't changed.

 

Also the HOB may have have nitrate rich water soaked into the media from when your nitrates were higher around 40 which when you hooked it back on mixed with your zero nitrates and gave you a reading of 5?

[Exodus]

Also the HOB may have have nitrate rich water soaked into the media from when your nitrates were higher around 40 which when you hooked it back on mixed with your zero nitrates and gave you a reading of 5?

+1

 

In my experience I have always found HOB & Canister filters to be Nitrate factories unless they are being cleaned, maintained, and media swapped out every 30 days or less (That's just my experience)

[VW_TDI_02]

+1

 

In my experience I have always found HOB & Canister filters to be Nitrate factories unless they are being cleaned, maintained, and media swapped out every 30 days or less (That's just my experience)

Well, they aren't really factories since the filters themselves aren't adding any nutrients into the water. It comes down to what you said about keeping it clean. If you allow detritus to build up in the filter then it will be eventually converted into nitrates. By replacing or cleaning the filter regularly, you are getting rid of the detritus and therefore aren't letting it build up. If you think about it, the same amount of nutrients is going to be in your tank regardless because it is coming from the food you add to the tank and not from the filter. The detritus is either going to break down in the filter or break down in the tank. The only way around this is to actually get the detritus/nutrients out of the water column. This can be done by replacing/cleaning the filter media, algae scrubbers, protein skimmers, etc.

[Mrkrsll]

The thing I don't understand is that the filter was cleaned very well and new filter floss was put in strictly to catch debris, but after just a few hours, the nitrite levels started creeping up. I removed the filter and withing 6 hours the nitrite levels went back down.

I am planning on getting a skimmer, but still up in the air about a refugium/sump so this is really the only way I have besides water changes to remove the debris out of the water.

 

I guess i'll remove the HOB filter and let the beneficial bacteria in the tank do its job while doing my regular water changes until I get a skimmer?

[Polarcollision]

Don't know for sure, but here are some ideas for you:

 

Running with the idea that the HOB filter is correlated but not causative...It doesn't really make sense that a clean filter would increase nitrites.

 

Stirring up the sand released partially decomposed stuffs into the water (w/ nitrites) that were eventually processed. Just a guess with little info to go on

 

Another idea. When I was reading up on everything that could go wrong with a denitrator, one thing was the possibility of producing nitrites if the flow encouraged sulfur bacteria instead of dentrification bacteria in the anearobic chamber. So... if you happen to catch a rotton egg smell, slowly clean and replace your sand.

[Mrkrsll]

Thanks for all the input and advice!