Nitrates still high after 50% water change

[sparky727]

my tanks been cycling for over 4 weeks. I have a 45 gallon cube, cycling with 40-45 lb live rock. I dosed stability for 8 days. My ammonia and nitrite have been 0 for 2 and a half weeks and my nitrate has been over 100 for that time since. Today I did a 50% water change trying to get my nitrates down and was going to do another tomorrow. I tested my water shortly after and it was still reading over 100 ppm on my salifert nitrate kit. I tested my rodi saltwater I used before it had 0 nitrates. All that’s in the tank is 10 hermits, I have plenty of algae. I’ve been waiting and was hoping this 50% would knock my nitrates down a little but it didn’t. Should I do another water change or what should I do?

 

[Idoc]

Knock out another 50-75% water change! That's the fastest way to decrease nitrates directly after a cycle!

 

[sparky727]

Ok cool thank you. Will do tomorrow

 

[Brandon Pantzlaff]

How did it go? Having the same problem right now. I have done 3 50% water changes and my nitrates havent dropped under 100 ppm with my salifert test kit. Today I added some cheato to hopefully drop my nitrates! Fingers crossed. Happy reefing

 

[Lasse]

If high NO3 concentrations are detected in a cycle or just after a cycle is done - it will normally be caused by readable NO2 levels or a defect test. Especially if large WC has been done.

I assume that the water used in WC is free of NO3.

Sincerely Lasse

 

[sparky727]

Water used in WC read 0 nitrates. My water is reading 0 nitrites and still 100 ppm after 50% WC yesterday. Doing another 50% today.

 

[chris k.]

Go bigger than 50% i did a 90 % wc after my cycle was finished and still left me with 10 ppm nitrates.

 

[sparky727]

Ok got it. Thanks

 

[Lasse]

Water used in WC read 0 nitrates. My water is reading 0 nitrites and still 100 ppm after 50% WC yesterday. Doing another 50% today.

In that case - confirm your measurement with another test or by this way:

Prepare 5 litres of new nitrate free saltwater. Mix and let it stand for one day - with aeration if you are able to have that. Try to be as close as you can to the salinity in the DT. It is important the the water should stand for 24 hours - IMO you can get a lot of funny measurements if you measure directly on new mixed saltwater

Test on DT water. write down the result. Mix 9o ml tank water with 10 ml of your new salt water mix. Shake it for some minutes. measure and read. multiply with 1.11 - write down the result. Next test 80 ml tank water - 20 ml new saltwater mix - shake and measure. Multiply the result with 1.25. -> 70 ml tank water - 30 ml new salt water - multiply with 1.43 -> 60 ml t water - 40 ml new - multiply with 1.67 -> 50 ml - 50 ml - multiply with 2 -> 40 ml t. water - 60 ml n water - multiply with 2.5 -> 30 ml t water - 70 ml n water - multiply with 3.33 -> 20 ml t water - 80 ml new water - multiply with 5 -> 10 ml t water - 90 ml n water - multiply with 10. If you still hav more than 100 ppm. Take 10 ml of the last mix - mix it with 90 ml of the prepared saltwater mix - multiply with 100 and you will get the real figures. If you do not - put the test in thrash bin ! From the point you get a reading below 100 ppm - you should be able to plot a straight curve of your measurement.

How did you the cycling? My 5 cents say - defect test

Sincerely Lasse

 

[sparky727]

My test is not defective. I’ve tested it on my tap water, my rodi water and my dt water.and had a LFS test to confirm I get correct readings. My water before it goes in to tank all reads 0 nitrates. It’s been almost 24 hours since water change I will go check levels.

 

[Lasse]

How did you do the cycle - adding ammonia, rotten shrimp or another method ? A 4 weeks old tank with real NO3 level at more than 200 ppm is out of my sight.

Sincerely Lasse

 

[sparky727]

I cycled it with live rock from an established tank same with sand. Dosed seachem stability and let the cycle ride out. Nitrates just staying at 100ppm. Doing 80% water change today most likely

 

[marvelousone]

what method are you using to remove nitrates. Skimmer, cheato.

 

[sparky727]

I’ve had my skimmer off my whole cycle. I didn’t know if I should turn it on now or not. I was just trying to reduce by water changes.

 

[Lasse]

Skimmer will not reduce an established concentration of NO3. But it is good to let it run for other reasons. If you not have ad any NH3/NH4 and your additatives not contain any - a concentration of more than 100 ppm NO3 is not likely.

Sincerely Lasse

 

[sparky727]

Ok well I’ve tested my nitrate kit in 4 types of water. 3 read 0. My tank water reads 100. I had ammonia and nitrite hence the concentration of nitrate. My test kit is not bad. I’m just going do water changes to get it down. I’m not here asking if my test kit works or not. I’ve verified and compared to others and with multiple water sources.

 

[Lasse]

I´m only saying that nitrates over 100 in a 4 weeks old aquaria started with RODI and when you not have add any external NH3/NH4 sources is not likely. I can explain this with formels if you want. To get 100 ppm (mg/l) NO3 in a 45 gallons you need to have added/produced around 3.6 gram pure Nitrogen as NH3/NH4-N - in one or another way. You say that you read 100 ppm - did a 50 % WC - still read 100 ppm. If that´s true - you must have had more than 200 ppm NO3 before the WC - more than 7 grams pure N. And this is if 100 % of the N has been nitrified. Is this likely?

Further - a NO3 test that show 0 in RODI or tap water says nothing when you use saltwater. There is tons of different ions that can affect the reading. Measuring NO3 in saltwater is a tricky thing. The same test can show different readings in different tanks because of different concentrations of ions that disturb the readings in different ways. Very small amounts of NO2 can disturb NO3 readings with more than 100 times. What do you measure your NO2 with ?

If you do a 80 % WC and your NO3 level is really 100 ppm - you should read 20 ppm after the WC - pure mathematic.

Sincerely Lasse

 

[sparky727]

okay I see what you are saying that makes sense. Thank you for explaining that. I thought they would have dropped to 50 as well if they were at 100. My salifert kit only goes up to 100 so maybe they were at 200. I’m doing another big change right now and hopefully I will see my nitrates dip below 100. I checked the nitrates in my mixed saltwater before it went into tank and it was 0. Then once in tank I get a reading. Maybe something in my rocks or sand.

 

[sparky727]

Ok I did an 80% water change my nitrates are reading 50 now. Idk if my rock is leaching nitrates in or if my nitrates were just insanely high. But will test again tomorrow and might do another water change after work.

 

[Lasse]

No way that rocks can leak NO3. You can get NH3/NH4 from the breakdown process of organic matters in the rocks that will be converted to NO3 through the nitrification cycle but rocks can't bound pure NO3.

Sincerely Lasse