Perfect Water, Still Weekly Water Changes? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 8 Old 08-08-2010, 02:57 PM Thread Starter
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Perfect Water, Still Weekly Water Changes?

I've had Ammonia - 0, Nitrites - 0, Nitrates - 0 for a full week now. My tank has finally cycled. Do I still need to do weekly water changes?

I've had the tank up and running with my fish in it for 41 days. I don't mind doing the changes at all, it's a small tank. I just wanted to know if it's necessary when the water is already perfect. I'm gonna add new fish soon - a shoal of 4 corys most likely - and I'll have to do larger water changes until the bacteria can keep up with the bio load. I'm also going to add more plants and make it a heavily planted tank.

10 gallon, filter, heater, mopani wood, 5 java ferns, 1 male Betta fish.
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post #2 of 8 Old 08-08-2010, 03:00 PM
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yes, weekly water changes are crucial to the health of fish. New (treated) water is the most healthy thing for our fish.

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post #3 of 8 Old 08-08-2010, 03:04 PM
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Originally Posted by wavebeast View Post
I've had Ammonia - 0, Nitrites - 0, Nitrates - 0 for a full week now. My tank has finally cycled.
Its curious you have 0 nitrates..... what type of test kit do you have?
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post #4 of 8 Old 08-08-2010, 03:07 PM
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i would do the weekly water changes the fish are happier and less stressed and most of all always healthy that way. if not at least do Bi-Weekly (weekly is ideal though)
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post #5 of 8 Old 08-08-2010, 03:39 PM Thread Starter
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API Master Test Kit. Liquid drops into test tubes. I know I'll need to change the water - I was just wondering. Because the object of water changes is to remove any Ammonia and Nitrites and keep the Nitrates under control. Well according to the test kit - I have none of those.

I'll probably do weekly changes despite what my test kit tells me because I'm afraid of allowing the bad levels of toxins to come back. I just wanted more information. It's most likely because I have 5 java ferns and only one fish in a 10 gallon. The ferns feed on Ammonia, Nitrites and Nitrates. Thanks for the help.
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post #6 of 8 Old 08-08-2010, 03:51 PM
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Yes there is a good chance with only 1 fish and 5 decent size Java ferns you will not have much beneficial bacteria, basically what you have done is cycled by the plant method. Which means there really is no actual bacteria cycle going on, be careful adding fish it could start a mini cycle once you have more fish then there are plants to absorb the ammonia from them. Your 4 corys would probably defiantly cause this to happen, if at all possible, add more live plants when you add your fish, so your mini cycle will not be as bad.

I also agree with the above, keep doing water changes even if you have no readings, you might be able to get away with doing 1 water change every week and a half to two weeks, but for optimal health of your fish freshwater is always appreciated. Of course once you put your corys in you will have to do multiple water changes per week based on your test readings until the mini cycle ends.
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post #7 of 8 Old 08-08-2010, 04:01 PM
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And also since you have such a small tank if you do add fish be careful the cycle will go faster and require more frequent water changes! But seems like your doing everything just fine!
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post #8 of 8 Old 08-08-2010, 06:28 PM
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One important point missed so far is that water changes are usually absolutely essential and have very little to do with the nitrification cycle (which is what ammonia, nitrite and nitrate relate to).

First, let me mention that in a heavily-planted aquarium with a moderate fish load, the plants will take care of things. But a regular weekly water change is still not a bad idea, just in case; sort of like insurance.

Leaving plants out of the picture for the moment, water changes depend upon the fish--what they are and how many--in relation to the water volume.

In nature, no fish lives in the "same" water for more than a second. Water is always changing--streams, creeks and rivers flow even if slowly, and in lakes and ponds there is water movement through thermal stratification and the percentage of fish to water volume is vastly less than in any normal-stocked aquarium. Same holds for streams, etc. The fish are constantly in "new" water. And that water itself is being "changed" by nature--rain and snow melt, evaporation (which is very high in the tropics), etc. If the fish don't like something in the water, they swim away somewhere else. That option is not there in the aquarium, they are truly captive, forced to contend with whatever we create. And water is far more significant than air in this respect. An animal in a cage has constant circulating air; a fish in an aquarium is in a confined space that is only going to improve if the aquarist does a water change.

Fish release pheromones into the water, and some of these affect other fish in various ways. Waste products are broken down by bacteria, but they remain in the water in that state until we remove them. And no one who performs weekly water changes of 40-50% can fail to notice the improvement in the fish's activity and behaviour after each one.

"Perfect" water does not exist in any aquarium. No filter can remove the above substances; filters only circulate the same old water around and around. Nitrification bacteria colonize surfaces and handle the measurable nitrogen states--having zero ammonia, nitrite and nitrate is fine, but that is only one part of the story. You cannot measure the above substances, but they are there, adversely affecting every fish in the tank.

Those aquarists who only do a water change when nitrate is high are already doing too little too late. By the time nitrates reach "high" levels the fish have been weakened by what is causing them to rise.

A weekly water change is crucial to the health of an aquarium. The more plants and fewer fish, the fewer water changes because we are allowing nature to do what it does best, but this is very limited in our aquaria. The volume of water changed weekly will depend upon the fish and aquarium capacity, and plants too. For 15 years I have changed 50% of my tanks every week, and I have several to do. But I would not jeopardize the health of my fish by failing to do this task.


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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