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High ph and nitrate

3852 Views 41 Replies 10 Participants Last post by  Ckalisz
Just got the API master test kit to test my aquarium. My ph was 8.4 and nitrates were 80-160. My tank has been established for years. I just started putting plants in over the last couple of weeks and dose excel and iron daily plus flourish every 3rd day or so. Just cleaned filter n sponge but not carbon or bio max three days ago. Did a 40% water change yesterday.

Tap water ph was 7.6
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I battle high nitrates in one of my cichlid tanks. So not to sound insulting but do you follow the instructions for the nitrate test. Like follow perfectly with all the shaking etc. etc. That is very critical. Have you tested another source to see if you're getting 2 different readings?
No offense taken. Yes I did follow and I tested my tap water which was zero and my sons 60g tank which was also high like my tank. His tank is pretty well stocked with large fish and he's not big on water changes. I just started taking a little better care of my tank and it is under stocked as of now.
Which Flourish product are you using? Some have nitrogen.

A non-planted tank will show rising nitrates until you do a water change.
Every bit of food you add supplies more nitrogen that will get turned into ammonia and nitrites, but you don't want to see these! Then it gets turned into nitrate, which is the safest of these. Rising nitrates means you have a healthy bacteria colony, but need to do more or larger water changes. I would keep on going with the water changes. Either moderate ones daily or every other day, or larger ones weekly, or twice weekly.
Plants are not going to magically remove the NO3 overnight. While plants do use some nitrogen, it is not that much that they can correct a tank with that high NO3.
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pH is not a stand alone value. It is controlled by the minerals and other things in the water.
One of these can be CO2. If the tap water has high CO2, then the CO2 leaves the water when you fill a glass or a tank. It may take 24-48 hours. High CO2 usually will drop the pH. When the CO2 leaves the pH rises. So you see lower pH when you first run the tap, and the pH rises over a day or two when the water sits exposed to the air.

If the substrate or decor is coral, limestone or any related rock then this can release minerals to the water that will raise the GH, KH and pH. This might not be a problem if you want to keep hard water fish. Most live bearers, many Rainbow fish, and Rift Lake Cichlids are good examples of fish that thrive in water with high GH.

For more help with the pH can you post more information:
What kinds of fish are you keeping? Do you want to breed them?
What is the GH and KH of the tap and of the tank?
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Great info hopefully I can give you what u need to help me some more. As far as nitrates I have just started with water changes over the past month and befor that I about never did them so I can agree that is a huge issue.

With ph I can't test gh or kh so I won't be able to give you those stats. I have never had an issue with fish including an angel til recently. I can't keep neon tetras alive and I just got a beautiful platinum angel who died in a week. I really want the angel to survive badly. I also have 4 Cory's, 6 zebra danios and 6 (brain fart can't remember what they are called) and they are all fine. I have standard aquarium gravel for a substrate. I plan on removing that tomorrow and putting in black diamond sand.

I have been dosing excel and flourish iron daily and flourish comprehensive every third day or so.

I wonder if lack of co2 could be an issue? I have fairly high light over half the tank(2x65watt coralife fixture) and a standard 15w t5 over the other half. It's a 55g tank. I just yesterday turned of the blue bulb of the coralife fixture.

Thanks for the input

Oh ya other 6 are odessa barbs

I also have a Texas holy rock in the decor if that helps any
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8am this morning


12 noon


Over 50% water change. Tank scrubbed new substrate. Nitrates still 80 to 160 and ph down to around 8 - 8.2.

Removed holy rock only left a WELL aged piece of drift wood and plastic decor piece until I can get a nice piece of drift wood.
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Might benefit with more plants in the tank. I had water sprite in a heavily fish stocked 10gal with CO2 and it thrived (nitrates were still barely detectable with Tetra test strips <10ppm). Once I removed a lot of the fish it stopped growing.

Now I am adding KNO3 daily and its doing well.

Water sprite can absorb nitrates directly from the water column and is quite hardy in a low tech tank. See if you can get a few cuttings and try it out. It should do well in your tank and help with the nutrient issue.

I would cutback to Flourish once a week as a source of micros only. It has NPK too which you do not need.
do an 80% water change. If you changed out the substrate recently it won't matter because there is no bacteria in there anyway. If you have time for an 80-90% water change it would help a lot and hopefully get your nitrates down to 20-40
The % of water change will yield the same % reduction in nitrates. So if you have 80ppm, a 50% change should give you about 40ppm. If you are not getting low enough, then you need to increase the size of the w/c.

How often and how much are you feeding. You should not feed more then once per day and skip at least one day per week. Many people only feed their fish once every other day.
I typically been feeding once and only a small pinch. Sometimes I'll put a second pinch in later in the day. They always act so starving. Since I cleaned the tank yesterday I threw an alage wafer in for my sae and my odessa barbs were on it like parannah on human flesh.
All fish act the same way. They will be fine. I have been on four vacations without feeding mine and all were fine when I returned. Almost two weeks each time.

Once you get your nitrates down about where they should be start testing before your water change and let that result guide you in how large your water change is.
Sounds good. I might try peat for my ph
Some filters will and some won't accomodate this but putting a small mesh bag of Peat in yur filter will bring down the PH but needs to be changed every few months.
I do the RO water thing to lower my Ph. I have no high range test kit but the blue is much darker than the blue at the 7.6 level in the low range test kit. So I'm guessing it's 8-8.4 and after you subtract the gravel and such the ten g tank is about 8.5g so
I take out 2g but put back 2g of tap + 40oz RO water(to account for evaporation)
and this gives me 6.8 Ph. It don't happenon the first water change. Since I change 20% it takes 5 water changes to get the 6.8
But since I only have two ten g tanks I only buy 1 g of RO water every two weeks
and use 5 x 8oz measuring cups of it in eah tank.
8am this morning


12 noon


Over 50% water change. Tank scrubbed new substrate. Nitrates still 80 to 160 and ph down to around 8 - 8.2.

Removed holy rock only left a WELL aged piece of drift wood and plastic decor piece until I can get a nice piece of drift wood.

Should/could not be nitrate levels you now see with new substrate unless filter is filthy or,,,test is perofrmed wrong.
leaving test vial's sit too long or not long enough ,not shakinh hell out of vial's can give poor result's,false reading's.
I actually used a timer that time to make sure I did the test properly knowing that I may have short cutted before. Filter was just scrubbed a few days prior but I'm sure it's due for a media change. Carbon especially.
How often and how much are you feeding. You should not feed more then once per day and skip at least one day per week. Many people only feed their fish once every other day.
I battle high nitrates as well and I would def recommend this. I feed every other day and my tank of 15 neon tetras, 2 differ types of loaches, ADCFrog, 2 Otocinclus, & 9 ghost shrimp are all thriving with my planted tank.
What's baffling me is that I just completely scrubbed my tank and changed my substrate and did at least 50 pwc. Probably more like 60 or 70 pwc. I tested my tap water again and it says zero nitrates. I'm afraid to do another huge wc for fear of wiping out good bacteria. I'm going to try swapping out al filter media. I've only rinsed the sponge lately so ill do new sponge, carbon, and bio max and see what happens
What's baffling me is that I just completely scrubbed my tank and changed my substrate and did at least 50 pwc. Probably more like 60 or 70 pwc. I tested my tap water again and it says zero nitrates. I'm afraid to do another huge wc for fear of wiping out good bacteria. I'm going to try swapping out al filter media. I've only rinsed the sponge lately so ill do new sponge, carbon, and bio max and see what happens
Swapping out all the filter media will also get rid of all of your bacteria because you changed the substrate. Dirty filter material doesn't directly lead to high nitrates. It's a byproduct of aerobic bacteria breaking down waste, and can not be consumed in normal aquariums.

I wouldn't change your filter media or you will have ammonia and nitrite issues that could kill your fish. In another two weeks you could clean the filter material in de-chlorinated water if you want. This will save much of the bacteria. I wouldn't totally swap out the filter material for another month at least.

Highly urge you to do another pwc.
I will do another big one tomorrow
To change everything in your filter would be a mistake after changing substrate also. Just keep up the water changes until you get it down. Once there it should be relatively easy to maintain a target range. Large water changes have very little effect on your bio filter as most of what you need is attached to things and in your filter, not in the water column.
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