Nitrates Steadily Increasing

[Kaidonni]

I've noticed that the nitrates in my tank are steadily increasing despite being cleaned every Sunday and Wednesday (~45 litres, 7-9 litre change). I do leave any water to be added for around 24 hours despite using Seachem Prime (I've always done this, it's what I'm comfortable with), and I'm wondering if that might be anything to do with it? Maybe I need to give the bucket a good wiping down with wet kitchen towel in case anything is staying inside?
 
I am in the process of rehoming a fish who is unsuitable for the tank (a Clown Loach), and I have five White Cloud Mountain Minnows, but it just seems to be getting worse after a number of weeks ago when it was lower. I did have a test result of 10-20ppm, but it's usually between 20 and 50, possibly higher (hard to read the nitrate Nutrafin Liquid test kit colour chart). I'm not sure if it's how I do the tests, the test kit or the test tubes (test kit new within 1-2 months), or if there have been fluctuations in the local water supply (today it was at 5-10ppm, but that doesn't mean much if there was a spike weeks ago). Tests usually show ammonia and nitrites at 0ppm, pH in the 7-7.5 range.
 
I even have to replace the polyster filter wool every single week now because it seems to break apart much easier than before (the Fluval 2-plus filter wool used to last up to four weeks), possibly because I'm cleaning so often - I didn't used to clean as often, just once a week. I do need to replace half of one of the two foam pads soon, it's rather full of holes; I've already eased in a new half since May - keeping the whole of the deteriorating pad at the same time to avoid any issues with ammonia or nitrite spikes - I just need to place in another new half to replace the deteriorating pad completely. Maybe that's it - too much filter media? Or I'm replacing the centre polyester pad too often (they won't last much longer than the 2-4 week mark in any case)? There is gunk within the filter housing, possibly that is causing issues?
 
Possibly over-feeding, maybe on pea for the Minnows or Pleco Multi-wafers for the Clown Loach - I feed every other day anyway, but have been tending to feed a small amount of cut-up de-shelled pea to the Minnows and one Tetra Pleco Multi-wafer to the Clown Loach every other feeding, with the remaining feedings flake food and catfish pellets.

 

[TwoTankAmin]

Nitrate basically enters a tank in any of three ways. The first is it can come in with our tap water. The second is that we may add it as part of fertilizing live plants. The final way is it is created as the end product of the cycle in tanks that have no denitrifying bacteria. I think yours is mostly internally created. I will usually suggest to folks that they do weekly water changes of 35 -50%. In your case that is just under 16 to as much as 23 litres. You are doing 1/2 to 1/3 of that. I would sugesst you increase the amount of your water change.
 
While you may feel better about letting your water sit and using Prime, it really is a case of wearing a belt and suspenders. There is really no need for both. The reason for letting water sit is to allow chlorine (not chloramine though) to outgas, which it will do naturally. But  dechlor makes this unnecessary. And some of the other things most dechlors now handle, like heavy metals, make their use more effective than just allowing the water to sit.
 
As for cleaning filters, floss is for removing gunk, it does this by trapping it. The more gunk it catches, the sooner it needs to be cleaned or replaced. If trapped organics are allowed to sit in most filters, they will have two negative effects. One is to clog them and flow is very important as it is the delivery mechanism for getting nutrients to the bacteria. The other is that, eventually, the organics start to break down further and as they do they become small enough to leave the floss (or other media) and get back into the water.
 
So when one cleans a filter you want to remove the trapped wastes in the mechanical media and then gently rinse out the bio-media as well. Clogged bio-media kills off the bacteria in it via starvation. The exception to this is when one has set things up to encourage denitrifying bacteria by using certain media designed to host these. A great example of this at work is in the Hamburg Matten filters which can go as much as a year or two and not need cleaning.

 

[DreamertK]

Those minnows are a cold water fish (water temp below 20C).
 
But you're only doing 1/5th of a WC weekly. Generally its best to do 1/4th or larger changes (11L). Once the clown loach goes, it should probably get better though. You should just make sure that the wafer is eatten within 3 hours or the peas/flakes eatten within the hour or 15 mins (or before they hit the substrate). You can also break the wafer into 1/4ths and feed that to see how much the loach likes to eat or just to cut down on it.
 
People will say you really dont need to worry about it so much especially since you're not keeping shrimps as long as it's below 40ppm, but it's still good to get those fish hormones and things we cant test/see out of the water.

 

[Byron]

One thing hasn't been mentioned yet, and that is cleaning the substrate.  Live plants are not mentioned, so I will assume there are none.  If correct, during your water changes vacuum well into the substrate.  All the organics that collect there will contribute to nitrates.  And I agree to increase the volume of water changes, even to 50% of the tank once a week.  I have been doing this for years, even though I have live plants; it makes quite a difference to the fish.
 
You want nitrates to never rise above 20 ppm, and preferably remain below 10 ppm.  If nitrate is also occurring from the tap water, this has to be factored in and dealt with.  Live plants would certainly help you here by using much of the initial ammonia so less gets moved through nitrite to nitrate.
 
Byron.

 

[TwoTankAmin]

Just an observation on nitrate levels. In the States the maximum allowable nitrate in municipal water is 10 ppm NO3-N. Note the -N part which means as measured on the nitrogen scale. If you have a water sample with this level of nitrate and you test it with a hobby kit, such as the one made by API, it will be reading using the total ion scale. As a rresult, if the test is bang on dead accurate, it should read 44 ppm.
 
While I know that nitrate levels can be an issue for tank inhabitants, I am not so sure about the level above which they should never rise. There is only one somewhat comprehensive paper I have I have read on this topic. It looks at all the literature for inverts and fish. It looks at a lot of things that will never see out tanks such as salmon, trout, and assorted water "bugs". But it does look at some things kept in tanks as well. If we focus on those species in the study that might actually be found in tanks, the numbers are interesting. If you are so inclined you can read it here: http/yaphankcivic.org/uploads/Nitrate_Toxicity_to_Aquatic_Animals.pdf

 

[Kaidonni]

Those minnows are a cold water fish (water temp below 20C).
 
But you're only doing 1/5th of a WC weekly. Generally its best to do 1/4th or larger changes (11L). Once the clown loach goes, it should probably get better though. You should just make sure that the wafer is eatten within 3 hours or the peas/flakes eatten within the hour or 15 mins (or before they hit the substrate). You can also break the wafer into 1/4ths and feed that to see how much the loach likes to eat or just to cut down on it.
 
People will say you really dont need to worry about it so much especially since you're not keeping shrimps as long as it's below 40ppm, but it's still good to get those fish hormones and things we cant test/see out of the water.

 
The first time I fed the wafer, I was terrified he wouldn't eat it all or much of it. I scared him off just trying to get it out of the tank, but found that leaving him alone a little longer was enough. As best I can tell, he plays around with the wafer for up to an hour, but he eats it all.
 

One thing hasn't been mentioned yet, and that is cleaning the substrate.  Live plants are not mentioned, so I will assume there are none.  If correct, during your water changes vacuum well into the substrate.  All the organics that collect there will contribute to nitrates.  And I agree to increase the volume of water changes, even to 50% of the tank once a week.  I have been doing this for years, even though I have live plants; it makes quite a difference to the fish.
 
You want nitrates to never rise above 20 ppm, and preferably remain below 10 ppm.  If nitrate is also occurring from the tap water, this has to be factored in and dealt with.  Live plants would certainly help you here by using much of the initial ammonia so less gets moved through nitrite to nitrate.
 
Byron.

 
I do have live plants in the aquarium, and only ever have. I also vacuum the substrate each cleaning, although not under the castle where the Clown Loach hides (to avoid panicking him), nor behind it. I try to be as thorough as possible, though.
 
At the moment, there's a planned 10 litre change tomorrow and one on Saturday, and in each instance I also always clean the filter out. I am hesitant to make too large a change for fear of causing temperature shock or pH shock (I don't heat the water prior to adding it).
 
I am of course curious if leaving the water that I'm adding to stand for too long leads to any increase in nitrates in said water.