Best time of day for testing aquarium? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 6 Old 08-25-2009, 12:05 PM Thread Starter
Best time of day for testing aquarium?

Is there a rule of thumb for the best time of day to test your aquarium for nitrate, nitrite, ammonia and ph?

I ask because I did a pwc 2 days ago. Today at 11:30 a.m. I tested nitrates which read 10 ppm and I tested nitrite which read between 0 and 0.25 ppm. Ammonia was 0 ppm. I have a heavily planted tank which I dose w/ macro and micro nutrients and I was wondering if my plants or the dosing of my plants alters the nitrite and nitrate readings during the day.

In short, should I test first thing in the morning before adding plant nutrients or does the time of day not matter for testing? Thank you in advance for your advice.
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post #2 of 6 Old 08-25-2009, 12:38 PM
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There are a couple of significant issues here.

Generally first, you should always test for ammonia, nitrite, nitrates, hardness and the pH immediately prior to a partial water change--if you test at all; it is not necessary to continually test all this once the aquarium is established. Testing prior to the pwc tells you the state of the water "as is" so to speak. I used to test the pH following the pwc, but don't bother anymore as I know what it will be. However, I sometimes test the following morning for hardness and pH, since I alter the water hardness very slightly (my tap water is absolutely zero hardness, and this causes problems with the fish's mineral balance) and this is to keep me satisfied that it is stable.

Second, testing for pH should always be at approximately the same time of day. This is because a planted tank naturally goes through a diurnal variation in pH. During the day, plants use the CO2 and the pH gradually rises; during darkness, plants and fish give off CO2 so it increases (slightly) and the pH drops [which is why aquarists with CO2 diffusion turn it off at night, to avoid a serious drop in pH]. Normally this is not a significant variation. In my planted aquaria [no CO2 added] it is about .3 or .4 max, from say 6.2 at 9 am to 6.5 or 6.6 at 6 pm. If you test at the same time every day, you will have a more accurate idea of where the pH is overall, and that is the important reason for testing. It should be fairly consistent aside from the diurnal variation.

Third, with respect to ammonia and nitrite, you should never have a reading above 0 in an established tank. If you do, something is causing it and you need to find out what it is.

With respect to plant fertilizer, exactly what type/brand are you using? Macro- and micro-nutrients are minerals and shouldn't have ammonia in them, but... one never knows. Plants require ammonium which they obtain directly by converting ammonia and nitrite produced by the fish and invertebrates and biological processes in the aquarium. The macro- and micro-nutrients, along with light and CO2, are needed in balance to allow the plants to photosynthesize.

May have more to offer when we know your fertilizer info.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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post #3 of 6 Old 08-25-2009, 02:04 PM Thread Starter
Hi Byron. Thank you for trying to help me again!

Dosing is as follows:

For macro nutrients I bought dry ferts and mixed up KNO3, K2SO4, KH2PO4 & MgSO4 into distilled water. I dose 10 ml for every 10 gallons of water on Sunday, Tuesday & Thursday.

For macro nutrients I've been using regular Seachem Flourish on Monday, Wednesday & Friday.

I've been using Flourish Excel daily however I do not dose anything at all on Saturday. On Sunday's I've always done 33% PWC. I used to do this with my old tank too.

The new 75g is only 5 weeks old, but heavily planted. I had added some established filter media from my 20 gallon into the canister of the 75 gallon about 4 weeks ago. Yesterday I removedthe old cut up filter media. I heard the canister can get clogged if you don't check it every month or so and I was worried the filter floss would block something (I've always had hob filters this is my first canister filter). At any rate, I wonder if discarding the established filter media has now left the canister with less beneficial bacteria and that's why I had a nitrite reading today. Again ammonia was 0 ppm though.

I did a pwc about 2 1/2 hours and I just tested nitrites again, I'm back down to 0. I guess I better keep a very close eye on this. Thank goodness I checked (for no reason). The fish were not in distress at all but I checked nitrates first. When I saw I had nitrates, I figured I better check my ammonia and nitrite levels immediately.
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post #4 of 6 Old 08-25-2009, 05:05 PM
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Thanks for this detail; that helps--and I see a couple of things.

First, plants require a number of macro-nutrients and micro-nutrients in order to photosynthesize which is how they grow by converting sugars into energy. These nutrients must be in balance, and the light must be sufficient (in balance if you like) to permit photosynthesis.

The "dry" nutrients bother me; are they specifically intended for aquarium plants? Or are they garden or house plant fertilizers (some people try these)? The nutrients aquatic plants need are different in their proportions to each other from land plants. And there are so many different nutrients that making up all of them and in the correct balance is very difficult.

Seachem's Flourish Comprehensive Plant Supplement has this required balance; you can see the list on their website. I would strongly recommend you use only Flourish Comprehensive. Some nutrients supplied in excess can be stored by the plant, but this depends upon the plant species and the specific nutrient; studies have shown that an excess of certain nutrients can sometimes negatively affect the plant's ability to absorb other nutrients, leading to poor growth and plant demise.

It is also very difficult to diagnose particular plant problems. Aquarists sometimes see yellowing leaves and immediately assume iron deficiency. While this can be true, there are a number of other deficiencies that can cause yellowing leaves. And more iron may cause other problems. Using a comprehensive fertilizer solves these problems because everything the plants require is there and in balance.

Flourish Excel is a liquid carbon supplement. I believe AuntKymmie uses this along with Flourish Comprehensive and likes the results; I don't bother with Excel because I stock my aquaria heavily (lots of fish) and they (plus the other biological processes ongoing in any aquarium) provide CO2 sufficient for the plants given the light and nutrients I supply. But using Excel is fine if you think your plants need it with your light.

On the question of the nitrite increase being the result of removing the filter floss from the canister filter--no, in my opinion. In a thickly planted aquarium, the plants remove most of the ammonia and nitrite before it ever gets to the bacteria, especially the bacteria in the filter which is far less than the bacteria colonizing all the surfaces including every plant leaf and every grain of substrate gravel or sand. Have a read of my post from Monday in which I went into this in detail, especially the last couple of paragraphs that deal with plant filtration:

Nitrates should be present in an aquarium, even a thickly planted one. Nitrates are not toxic to fish unless in very high numbers. Most authorities suggest that 40ppm is the upper limit for most fish (some can tolerate much more), but recommend 20ppm or less. In my aquaria nitrates consistently run between 5 and 10 ppm, and closer to 5 according to the API colour test chart. Partial water changes are the best way to remove/dilute nitrates; in a planted aquarium that is biologically established the nitrates will never be above 10ppm unless there is an adverse biological issue like neglecting regular pwc, overfeeding, or dying fish and plants.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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post #5 of 6 Old 08-25-2009, 07:36 PM Thread Starter
Hey Byron. Looks like you've been hijacked into helping me here. Thank you for taking time to post such detailed information. It is greatly appreciated.

The dry ferts were purchased from Green Leaf Aquariums by the pound. A ton of people on the planted tank forum use their products, so that's why I went w/ it. The plants are growing in BEAUTIFULLY though.

Today was the first time in 5 weeks however that I've had nitrites. AND, it's the first time I had a nitrate reading too. I had asked someone if 0 nitrates were a problem in a planted tank because my test always showed 0. I even calibrated the test to make sure that it was working, and it was.

I did a pwc on Sunday, however Sunday, Monday and today I was overfeeding my fish (for a reason). I noticed that one of my angelfish was getting very thin and I also noticed that it was barely getting any food. The other angels were gobbling it up before it could get anything. So I started overfeeding to ensure that the thin fish was getting food. I would try to vacuum up the food that fell to the gravel, but cleaning a planted tank is no easy task. I wonder if that caused my nitrite spike (plus all the excess poop from the fish that got extra food). I'll have to come up with another method to try and feed the poor slow feeding angelfish.

Thank you again Byron! BTW, yes I did read the post on fishless cycle or non fishless! Always great info from you.

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post #6 of 6 Old 11-03-2018, 01:52 AM
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Goldfish advice please!

Hello, I have two goldfish ( oranda and black moor). I have had them for 1 month and have been doing my best to take good care of them. In the beginning my oranda seemed to be the faster and the greediest of the two, always pushing the black more out of the way but recently he's been displaying opposite traits. These past 4-5 days he's barely eating or chasing my other fish, and my black moor ( which is smaller) is now running the tank. My oranda also has barely been pooping and when he does it's white and stringy. He also has a flat white freckle on his head and I'm concerned what this could be a sign of. I've gone to the aquarium shop to show videos, ask questions and purchase products and though he is still swimming , attentive and friendly with me , he has changed in his behavior . What should I do?
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