Strange Nitrate problem in fishless cycle

[MJ 1044]

Could an experienced hobbyist please help me with my fishless cycle.
For the last 4 days my tests indicate that my tank is cycled. Zero ammonia and nitrites after adding 3 or 4 ppm ammonia the day before. The problem is with the nitrates. Looks like the tank is cycled with -0-ammonia and nitrites and I do an almost complete water change due to the nitrates testing at above 80 ppm. This reoccurs each day, and I can’t understand the NITRATE problem and why it keeps coming back.
I use RO water that is re-mineralized with Seachem Equilibrium. Seachem states that “Equilibrium does not contain any nitrogenous pollutants (ammonia, nitrite, or nitrate)”. I have tried to keep the PH up in the alkaline region so as to not stall the cycle.
Tests on my RO water show no nitrates.
Thinking that since my PH drops overnight from alkaline to slightly acidic I test for KH and it is in the range of 50 or more ppm with GH somewhat less than 100 ppm.
Using a 10 gallon tank with a Aquaclear HOB filter. Could there be something in the sponges that is raising nitrates? Will I have to start a new cycle?

 

[Aiken Drum]

Are you saying the nitrate keeps coming back when you arent redosing ammonia after your water change?

Most of the time nitrate is the end result of the nitrogen cycle. Ammonia turns to nitrite. Nitrite turns to nitrate. Nitrate is removed by changing water for clean water. Having nitrate in a cycled tank is normal. You will see nitrate rise steadily until you do your regular water change to bring it down again. After which it will steadily rise again until your next water change. Etc etc.

Every 1ppm of ammonia turns to 3.7ppm of nitrate. So your daily 4ppm dosing of ammonia should see nitrate rise by about 15ppm a day. A typically stocked aquarium produces the equivalent of 0.5 to 1ppm of ammonia, so you would normally see nitrate rise by 2 to 4ppm a day.

There is a stage of the nitrogen cycle that involves anaerobic bacteria that consumes nitrate and producing nitrogen that offgases. But this stage is very difficult to achieve in freshwater aquariums. Plants also consume some nitrate, so its possible in a heavily planted but lightly stocked tank to have low nitrate levels.

 

[MJ 1044]

Thank you for your reply. What I can't grasp is why my nitrates are 80+ ppm after an almost 100% water change. I realize that dosing ammonia (prior to adding fish) will raise the nitrates a little (15ppm as you indicated).

 

[Aiken Drum]

Are they back up high immediately after a water change? Or do they gradually rise again over a period of time?

Have you tested your new water for ammonia and nitrite?

Is there anything in your aquascape that might be an ammonia source? Like a soil based substrate?

Yes sponges trap detritus that decays and can contribute to nitrate. Periodically rinsing them in dechlorinated water to remove this detritus should be sufficient, and this shouldn't be happening in a recently set up system.

 

[MJ 1044]

Almost nothing in tank and my fresh water tests 0 for ammonia, nitrites and nitrates.
Could a stalled cycle at some point kill beneficial bacteria in the sponges of my HOB and raise my nitrates?
There is almost nothing else that could contribute to nitrates which is why I am confused. I am thinking of just cleaning everything and starting a new cycle again.

 

[Aiken Drum]

Your cycle isnt stalled. You dosed ammonia and nitrate is coming out the other end. If your cycle was stalled there would be no nitrate.

If you are seeing nitrate there is an ammonia or nitrite source and the cycle is turning to nitrate or there is a nitrate source.

Or there is something wrong with your testing.

I would get a 2nd opinion on your water tests. What test kit are you using?

Do a 100% water change. Report back on the results immediately afterwards. Then report back again after 24 hours.

 

[MJ 1044]

Do a 100% water change. Report back on the results immediately afterwards. Then report back again after 24 hours.

I have done a 100% water change for 4 days in a row with the situation occurring each day and I know my fresh water is fine.
I just happened to have on hand brand new API ammonia and nitrate test kits but no nitrite test kit. I did have new API test strips so I used that for nitrite test. The results are the same.
I have to believe there something in the filter sponge.
I am going to clean everything and start over.
I do appreciate your help and advice!

 

[Aiken Drum]

Really dont clean everything and start over. You are misunderstanding the situation. You are cycled. There is no need to do this.

Just do what i suggest. 100% water change. Tell us the results immediately afterwards. Wait 24 hours and tell us what the results are. Lets diagnose the issue.

 

[Andy Sager]

Almost nothing in tank and my fresh water tests 0 for ammonia, nitrites and nitrates.
Could a stalled cycle at some point kill beneficial bacteria in the sponges of my HOB and raise my nitrates?
There is almost nothing else that could contribute to nitrates which is why I am confused. I am thinking of just cleaning everything and starting a new cycle again.

When in doubt, always have your test results checked by either another test kit or at a local shop that tests water. Your test results could be wrong.