Tank Nitrates Lower Than Tap Water.

Good afternoon,

The water in my area has fairly high nitrates:  25ppm according to my supplier’s website and somewhere between 20 and 40 with the API kit (I struggle to differentiate the almost identical shades after 20!).

To keep the levels under control I have been doing weekly water changes of about 36%, but up to now it’s still been quite high after 7 days (definitely over 40).  My filter media is supposed to support the nitrate eating anaerobic bacteria, but it seems they propagate very slowly so to keep things manageable in the short term I purchased JBL BioNitratEX which is supposed to help control nitrates biologically.

They recommend one bag of stuff per 50 litres to remove nitrates, and since I only want to keep them under control (my plants need some) I used one bag in the filter of my 120L tank.  I won’t be able to change the water on Friday as usual this week, so I tested today to see if I need to change the water early, or leave it until Saturday.  The tank levels are now lower than my tap water!!

How will this affect my water changes?  Is a sudden rise in nitrates when I add fresh water going to distress the fish?  Can (and should) I extend the intervals between water changes?

Thanks

I don't find it a huge problem and the fish are fine with water changes - don't forget that you are not changing all of the water, so it's not as if your water is suddenly going to go from 0 to 25ppm. With partial water changes the levels will only change slightly.

Good point.  Why didn't I think of that?

I think I'll reduce the amount I change this from 40L to 20L and keep a close eye on things.

@TrenchyLs 

We get our tap water from the same supplier as  @Littlefish.

When we first set up our tank, last November, the stubbornly high level of NO₃ was a concern.  However, that high level reduced, eventually, to between 5ppm and 10ppm.  This reduction occurred quite smoothly from 50ppm to 40ppm in December, 30ppm by the end of January and then 15ppm by March.

I'm convinced the NO₃ eaters just took a while to kick in.  We don't have live plants, probably just as well!  We do a 20% water change once a week and tend to do parameter checks after the change.  On the odd occasions we do check before and after, the NO₃ before has always been about 10-15 ppm above the after level.  So, having reduced quite gradually over the 6 months, the "shock" to the fish is around this 10-15ppm before and after the weekly change.

We have an 80L tank with 19 fish, stocked to 70% according to the Community Calculator tool.  The only real losses we've had are a couple of Mollies and 12 Black Molly fry that appeared as an added bonus.  The later having popped off over time in ones and twos.  We haven't found many remains of the fry so think someone in the community is not quite as "peaceful" as was made out to be!

 

Just adding some info as the main concerns have been well answered.

It takes around 6 months for an anaerobic bacteria colony to establish in a filter with suitable media but it's well worth the wait.  Suitable media is a highly porous material (40% plus porosity) such as Alfagrog or Biohome.  The anaerobic bacteria builds up in the centre of the material over time.  In general, because of porosity, these are a better option than your ceramic rings etc. because of the area bacteria have to grow.

I was confused a lot about the different levels of 'safe' nitrate that appear on many websites so I've spent a lot of time reading up on the subject.  Nitrate of 25 ppm mg/l from tap water isn't too bad.  Nitrate can be tricky as the tolerance is on a fish by fish basis by species as well as the individual.  More sensitive fish like dwarf cichlids, discus, panaques, etc. wouldn't be at their best in 25 ppm nitrate water and will be susceptible to illness.  They're more used to living in vast amounts of flowing water keeping nitrates very low (around 5 ppm).  Goldfish on the other hand are used to ponds with barely any flow and have a very high nitrate tolerance (I've seen 1000 ppm stated and can easily believe that).  Most other fish lay somewhere between that range.  I've looked hard and have been unable to find a species by species list which is a shame as that kind of knowledge would save a lot of fish.  A lot of sites say around 40-50 ppm nitrates is when fish will be affected by nitrates but that is a general catch all for most fish species.  If you ever see the words 'needs good water quality' describing fish care you need to keep those nitrates well down.

 
Following up on the conversations from 10 days ago, when I did my last 20% weekly water change yesterday, I checked the before and after parameters, just to see what our NO₃ levels were.

Before the change, NO₃ was at 15ppm.  After it had gone down to 5ppm, spot on with my earlier remarks.  The funny thing is, out-of-the-tap shows as 10ppm.

This is the infuriating thing about this water-keeping lark.  If I start of with 100% of the water at 15ppm, take out 20% and replace it with off-the-tap at 10ppm, no way, mathematically, should I get a new reading of 5ppm. 

Logically, it should be somewhere between 15ppm and 10ppm, by my calculation, 14ppm.

Now it could be my test kit playing up (NT Labs 2 reagent liquid test) which would be a bit weird since even if it was inaccurate, all these readings taken over the space of about 30 minutes should at least be consistent with each other.  Or the granularity of the colour chart showing readings for 0, 2.5, 5, 10, 20, 40 & 80ppm is too coarse for me and Mrs Adenann to tell if the readings we get are 5, 10 or 20.  The reading we get of 15ppm is, obviously, a bit of a guess as the reaction colour is darker than 10 and, we think, lighter than 20.

I can't get too upset by all this as, when we first started the tank last November, the 2 x MAs, P@H and 2 x independent LFSs round here all said they use water off the tap and do nothing to it with respect to NO₃.  Their take on it is "it is what it is and as long as it stays fairly stable, who cares?".  At least two that I know of don't bother with testing customers' NO₃ at all.

@Littlefish , I recall we had discussion around this topic, amongst others, when we first started out as you're on the same water supply as we are.  Have you checked your off-the-tap parameters lately, and specifically, what do you see for NO₃?

Does anyone know of a test that would accurately measure the level, say, to the nearest ppm?
 

It's very easy to get caught up in the numbers, isn't it?

Doesn't help when anything over 20-30 looks the same to my eyes!  Plus, it makes a huge difference where you hold the tube while checking the chart.  If I hold a tap water test against the white part of the colour chart it goes bright orange and looks like it's about 80 (which is unlikely).  So now I check in the bathroom since the lighting is consistent (no window) and the white tiles mean I can see the colour without it becoming too intense!

I'm starting to relax about them all now though since everything is stable, the fish all seem happy and you guys have reassured me that the fish aren't all going to die with a slight fluctuation in the nitrate!

I still test at least once a week tough, especially as my stock changed slightly last week.

@Sue  How often do you test for ammonia, nitrites and pH then?  I find pH testing really irritating since mine sits around the max of low range and min of high range so I always have to do both tests to make sure it's still in that crossover value of about 7.4 

or if I forget to turn the filter back on and only realise next day - I've done that several times  .

I've manged that a couple of times myself as I turn the filter off when feeding. Luckily it's not been left off overnight (yet) since the tank is about 3 feet from the bed and I noticed the lack of humming when I try to sleep!

I tend to leave a door of the base unit open now as bruised shins are a good reminder to turn the filter back on!

 
@Sue
Thanks.  Seems like you, me and all the LFSs round here are in agreement about the importance (or not) of NO₃.

@TrenchyLs
I've just, at last, posted a review of the NT Labs Aquarium Labs test kit I use.  The main reason for my choice was exactly the problem of a pH around the 7.5 mark and low/high range tests.  The NT Labs pH test is a single broad range test, that covers from 4 to 10 in one go.  That has it's own drawback though.  See the full review at Tank Equipment Reviews / NT Labs Aquarium Lab Multi-test Kit.

Just to chip in on Sue's reply about test frequency, We're not experienced / confident enough to let things go for as long as Sue does, yet.  We've been at this for only 7 months and still do a 20% water change every week and NH₃, NO₂, NO₃ & pH generally after each change and occasionally a before and after set to see how much the week's worth of fish activity has changed things.  Some would say perhaps I should be doing only 10% a week or 20% every two weeks, but we (and the fish) are happy with what we do for now.

I was so anal about the numbers I used to do multiple tests, Tetra Strips (not very accurate), JBL, SeaChem NH₃ & pH alarms (which don't work for me for some reason) and weekly pestering of my local MA.  Now I've calmed down a bit!  Just the NT Labs kit weekly.

I've said it before, elsewhere, that the manager of an award winning LFS told me very early on that we're not fish keepers, we're water keepers and the fish just get in the way!