I am very particular about my water tests and maintenance. Lately I have a trend that has changed (nitrates) and I'm wondering what has happened. Amm & Nitrate are always zero. Ph always 7.3; temp maintained very steady between 79-80F.

Tank = 135 gallon; stocking levels 2 young O's, 3 clown loaches, 1 young sev. I only feed what they will eat; and even though the O's are very messy eaters - the loaches are a great clean-up crew. Filtration is Eheim Pro3, no carbon.

I perform water tests every three days or so using API liquid test bottles.

The trend over the past 3 months has been after 6-7 days I get a Nitrate reading of 10-20; I do a 25%-30% water change regardless of readings every 6-7 days.

Over the past two weeks, I've started getting Nitrate readings of 40+ after only 3 or 4 days. It's been as high as 40-80 after 6-7 days.

This week after only 4 days; Nitrate was 80! I did a 25% water change immediately; waited an hour and then read Nitrates at 20. Tap water is between 0-5.

What would cause my nitrates to creep up - when after months I typically max out at 20-40? I'm stumped. Am I not changing enough water?

thanks in advance

as your tank come to ages, fishes grows and produces a lot of waste.
the mere fact that you are getting zero for ammonia and nitrite, it
means your filter is doing well when you got high nitrates. hitting a
40ppm marks and above requires a large water change and you will be fine.
your system is working perfectly.

thanks Paul - should I be doing a larger water change? I currently do 25% - perhaps I should do more.... like 40%?

after changing 25% and having the Nitrates not drop as much as I would want is making me think I need to replace more volume with the water changes.

whenever your nitrate hit 40ppm and above, 50% w/c is recommended.
your ammonia and nitrite at zero means you have efficient bacteria
converting the two into nitrate...the reason why it is jacking up..
as long as you pH is stable, your fishes will be fine.

x2, i do a 50% waterchange weekly and my fish stay happy.

nitrate levels shouldnt be that bad for the fish.. of course keeping it low is the motive.. but as far as I know the entire nitrification process would be fine since you have a zero Ammonia / nitrite level..

the only .. rather easiest way to remove Nitrate is to change water.. I guess just for now.. you can change 10% water everyday.. should be fine

I certainly agree with Paul. High nitrates accompanied with no ammonia or nitrite indicates a healthy biological filter. Having said that a dirty filter could possibly make your nitrate raise a little quicker throughout the week. Also, increased feeding will also make your fish create more waste which will in turn results in nitrates raising that much quicker.

80 ppm is rather high and I certainly wouldn't like to be leaving it like that for too long. Just increase the size of your water changes slightly and you should be able to control them without any problems whatsoever

Sorry, I'm just repeating what everyone else has said, but no harm in that I suppose.

thanks everyone!

Penn - actually you made me think that I may want to rinse my filter media (in tank water of course:) this coming weekend will be a month since the last rinse & clean of the mechanical filter. I do this once a month - is that frequent enough? I'll see if that makes my trend go back to normal.

I'll also step up my weekly water changes - instead of only changing 25%; I'll do 40-50%

Another possible reason could be a dead fish. This would lead to an increase of ammonia and thus nitrates? This is why it is always a good idea to do a daily fish check while feeding along with a visual check for dead fish.

MeghanR wrote:


Definitely a good idea to keep a check on the filtration since it plays a very important role on your system. The problem with not cleaning filters on a regular basis is three things can happen and have happened to me in the past. Excess waste will definitely increase the chances of poor water quality, definitely high nitrates and possibly ammonia. Small filtration systems also get clogged very quickly if not cleaned on a regular basis.

My first aquarium was the Trigon 350 with the internal filters only. Even leaving the filters for just over a week without cleaning meant they became absolutely clogged with horrible gunky crap. I had a couple of Eheim 2028 canister filters on my 125 gallon and I could leave plays for about two or three months before they became full of sludge and needed cleaning.

The 75 gallon sump I have are my 300 gallon can be left for months and months without cleaning and I don't have any water quality problems whatsoever. Problem is, when it does come to cleaning it is one hell of a job. The new sump that I will be installing shortly will have drainage holes installed so I will be able to flush it all out rather than having to remove all media.

delboybully wrote:


definitely not a dead fish - I do a "head count" every day - LOL

I think it's clogged filter - not completely clogged, but definitely not at normal flow. I'm going to rinse/clean tomorrow for sure and see if that does the trick! I'm going to bet that it does. thanks again everyone for the feedback.

Penn - sounds like having drainage holes on the sump will be most excellent

I notice a change in my nitrate levels. at times my tap water can be as low as 10pph and on another day it will read 20pp. I have gone back to filtering all my tap water again to reach 0pp before i use it to do a water change. by doing this over the last few wks i notice my nitrate levels drop to 10pph or less with only one 30% water change a wk.

i have also changed how often I clean my filter, i used to leave it a few months but this meant it put out a lot of nitrates. by bagging my media balls in fine net bags the bags work like a filter wool catching all the small bits. so I now do a clean once a month, rinsing the sponge and bags. this has helped in the nitrate drop too as it removes the crap before it gets broken down into nitrates.

I have never seen my nitrate level so low. given my tap nitrate is 20pph at the moment I am managing a tank nitrate of 5 or 10pph even though i am feeding the arow 3 large shelled prawns a day. anyone that struggles to get low nitrates will benefit from monthly filter cleaning even if the filter can cope with a few months without a clean. also a nitrate filter to filter the tap water. the stuff you put into your filter is rubbish and a waste of money, there are a few of these on the market so don't get caught out. if you want a decent nitrate filter go with something like this.

www.cleartides.com/page13.htm

add a small power head and you can run it on your tank. but don't miss out the water changes cos your nitrate is low. for £40 and a 1000+ recharge life with dish washer salt you could have low nitrates for a few yrs. i use a nitragone(not the model I posted a link to) and its still working after 10yrs.