Seemingly Neverending High Nitrates In Tanks

  1. Kesh88 Member Member

    I'm having some issues with seemingly never ending high nitrates in my 3 betta tanks. The problem started about 3 months ago, I thought I'd dealt with it over a month of daily water changes but seems to be back again.

    I have two 38L tanks and one 68L tank, each home to a single betta, live plants and some red cherry shrimp. The larger tank was a community tank but a few weeks ago I switched out all the fish for a single betta. Each tank is heated and filtered. I run two sponge filters in the smaller tanks, as well as a Hagen HOB filter on one tank to deal with some detrius issues I had in that tank. The larger tank runs an Aquaclear 50.

    I change a minimum of 25% of the water in each tank once a week with a gravel vac and Seachem Prime. Once a month I do a larger 50% water change. I've followed this routine for the last 4 years but have only just started having nitrate issues. The smaller tanks have been running for 4 and 2 years respectively, the larger tank for around 10 months.

    Last night the betta in the large tank jumped out despite it having a cover, I think he got out around the HOB filter. I'm not sure if it was the nitrate levels or just bad luck that caused him to jump but he didn't make it. Aside from this and losing another couple of fish recently after having them 1.5 years my fish seem active and eat well.

    The nitrate levels in each tank today are between 40-80ppm, despite yesterday's 25% water change. My tap water is usually 0ppm but sometimes it's 5ppm. My API master kit is not expired.

    What could be causing these constantly high nitrate levels and what can I do about it?
  2. Initiate Member Member

    large 50% water changes daily to get your nitrates down
  3. Kesh88 Member Member

    Will that only be a temporary fix though? Because I did exactly that when the problem first occured a couple of months ago. The nitrates evidently came back.

    I also think it stressed my fish out and killed one of them early. I read somewhere it might be better to do daily water changes but only of 10%?
  4. ThreadfinQueenx Initiate Member

    Do 50% water changes and syphon the gravel, wash decor, scrub algae ect ect and tetra nitrate minus is amazing for between water changes and it keeps the levels low. I'm not sure what could cause it but if you have any live plants could be the problem because they alter the water quite alot.
  5. Kesh88 Member Member

    I'm reading a lot of conflicting advice on old tank syndrome, which I think this is as the pH has also dropped. Many websites say do small daily water changes of 10% and here I'm being told daily water changes of 50%. So which is it 10 or 50%? That's a huge difference. I'm afraid to do 50% every day as last time I did that the nitrates went down but my one of my fish also died in after a couple of weeks.
  6. Initiate Member Member

    There shouldnt be problems unless your temp and pH fluctuates.
  7. Briggs Well Known Member Member

    If the fish have been in high nitrates that have built over time, you probably want to bring the nitrates down slowly so not to shock your fish, so smaller daily water changes might be better.

    As for the root cause, have you tested your tap water lately? There might have been changes made at your local water treatment plant that has caused a nitrate spike. If it's normal, how often do you do maintenance on your filters? A build up of detritus in you filter media might cause nitrates to rise.

    If you can't find the source of the issue, or it's something out of your control, I've found the best nitrate sponges are floating plants. They grow like crazy and you'll throw handfuls away every day, but a good chunk of nitrates will go with them. If you don't have any already, I'd look into some to see if any of them appeal to you.
  8. Kesh88 Member Member

    Thanks, I think it was the big water changes that killed my last fish. I have some elodea I can put in each tank. I've recently added some amazon frogbit to the large tank as well although only 3 small bunches.

    Also I rinse the filters alternately in old tank water every 3 weeks.
  9. Hill Dweller Member Member

    Like @Briggs I was going to suggest testing your tap water in case there has been any nitrate introduced that way.

    If the tap water has no nitrate, then managing the nitrate produced in your tank comes down to arithmetic. If you have a tank on 80 nitrate, then a 50% water change will bring it down to 40. Another 50% water change should see you get to 20. And so on.

    Do enough water changes to get it to say 10. Then wait a week and see what it gets up to. Let's say you start at 10, then in a week it gets to 20, then you know because of the maths you need to do a 50% change weekly to keep it at 10. Hopefully that's making sense? It could just be that by only doing 25% most weeks it was just building up.
  10. Briggs Well Known Member Member

    Yeah, I've heard horror stories about people who've had a tank for years and didn't realize they were supposed to do water changes. When a well meaning person tells them, they panic and do a 90% water change that ends up killing all their fish. Turns out they were actually doing okay in their liquid nitrogen before that because it had built slowly and they adjusted with it. Not a goal to strive for, certainly, but something to keep in mind.

    If your frogbit takes off, it'll do so with gusto and help to keep your nitrates in check. Any fast growing plant will help, but floating and emersed plants seem to do it best. Being so close to the light source and having easy access to CO2 in the air makes it easy to grow quickly. You could try something like pothos cuttings if you have a plant handy. It's a pretty common house plant. You just have to rig it so the leaves are up out of the water, and the stem/roots are in. It's less of a great idea if you have cats or dogs, though, as it can be pretty toxic to them if they happen to eat any.

    These are kind of bandaids, though. I hope you can figure out the source of the nitrates.
  11. Kesh88 Member Member

    Can't risk pothos with my cat that likes to nibble almost any vegetation he comes across! It's late now and I'm exhausted so will test my tap water tomorrow. I've done a 20% water change on all my tanks tonight just as a precaution, will work out the rest tomorrow.
  12. Briggs Well Known Member Member

    Yeah, it isn't usually deadly to cats, but it'll make them pretty sick. Best to avoid. There are probably other, safer plants that'll do the same if you want to try them. I know bamboo grows well out of aquariums, for instance, and should be harmless to casual plant-nibblers.
  13. TexasGuppy Member Member

    Would seachem prestine help here?
  14. 86 ssinit Well Known Member Member

    Ok I think the problem may be 3 weeks in between filter cleanings. I would recommend 10% water changes once a week and clean filter at the same time. The build up of 3 weeks is feeding the nitrates.
  15. 86 ssinit Well Known Member Member

    Another thing may be he test kit. If it’s api and you were not shaking the 2nd bottle enough the tests could be wrong. I’d been using the kit for years with no nitrate reading at all. A thread hear recommended shakeing the 2nd bottle like crazy and afte4 I did that bingo I had nitrates. But the chemicals in that 2nd bottle because of the earlier lack of shaking were giving me a very high reading. Bought a new one and all is well readings between 5-10 now.
  16. Kesh88 Member Member

    I've tested my tap water for nitrates, 0ppm. 88 ssinit I always shake the second bottle like crazy for a good 45 seconds.

    For now I've done a 75% water changes and cleaned the filters on all my tanks.
  17. TexasGuppy Member Member

    Just a guess here, what kind of substrate do you have? Maybe you are getting buildup at the bottom? Perhaps change it out on one of the tanks and see if the problem goes away. Since it's common to all tanks, it's worth a shot. Can you manually clean substrate well instead of changing? You may be able to use diluted bleach in a bucket, then rinse well and spread it out somewhere to dry really well (eliminates bleach).
  18. Kesh88 Member Member

    I use gravel in all my tanks and do a deep gravel vac at least once a month.
  19. Kesh88 Member Member

    Test results on all 3 tanks 24 hours after a 75% water change on each tank:


    *groan* why are these levels not dropping?!!!
  20. 86 ssinit Well Known Member Member

    That is strange. The 2 ends look 40 or more but the middle looks ok. What else is in the tanks? Shrimp?