Water Change Frequency 40gal / 15 fish < 1" each ?? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 7 Old 01-29-2007, 08:16 AM Thread Starter
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Water Change Frequency 40gal / 15 fish < 1" each ??

Relatively new to fish keeping here. Our fish seem to be doing pretty well.

3 strawberry tetras, 3 blueberry tetra, 2 pairs of guppies, and 3 red velvent swords. (Headed for maybe 20 to 25 total fish for this tank).

Undergravel filter - reverse flow Aqua Clear 50 powerhead
Power Filter - Emperor 2800

In reading the sticky information for new fish owners, I see recommendations for water changes at least once a week and maybe more. I was coming into this thinking water change of about 1/3 to 1/2 max every 2-3 weeks via syphon/gravel cleaner.
I would then change the powerfilter cartridge about a week later to minimize total shock on the tank.

So, how often should I be doing water changes? with or without gravel vacuuming?

One last thing... one of my female guppies just disappeared. Any clue as to who the culprit may be? It's strange as we've all been watching the fish quite a bit an no signs that she was sick and no signs that any fish were being harassed. Our lone baby guppy vanished at the same time.
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post #2 of 7 Old 01-29-2007, 09:26 AM
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hi there. u said u have 2 pairs of guppies?? it is possible that the female that has disappeared was harrassed by the males, ideally u should keep livebearers 3 females to 1 male. hope this helps
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post #3 of 7 Old 01-29-2007, 11:29 AM
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I do water changes weekly at 50% regardless of how many fish I have. Is the best way I know to keep anything from building up in the tank. Some change less often but that is what I have been taught and my fish have never been more colorful or happy. I also gravel vac every week at the same time even though I have a lot of live plants in two of my tanks. The plants still flourish. One tank tends to have a lor of mulm every week and one seems to have very little and the water is never dirty.

As for the filter, if you rinse the filter in tank water every week with the water change then the bacteria stay alive and won't cause any stress. I have modified my Aquaview filters I have on my nonplanted tank so that I can rinse the filter pad and it has worked fine ever since.

I have heard that the reverse flow eleiminates the need to do frequesnt water changes but I do have to disagree. Water changes are to remove dissolved solids that can not be removed any other way, not even with plants. With a 50% water change, whatever the levels normally are that are added to the tank weekly are removed and the most you can have is double that amount over any given amount of time if you change 50% weekly. If you only change monthly then whatever amount that can collect over a month is doubled. Anything less than 50% and the numbers get larger and larger.

Is the old idea of better safe than sorry, weekly 50% water changes prevent and major buildup and therefore your fish should be happier.

To give you an idea, I dose 30ppm of NO3 in my planted tanks a week. I change 50% weekly so even if my plants don't use any of it all then the most that can be in the tank is 60ppm. If I dose the same and only change 50% once a month than the most I can have 240ppm of NO3. Same goes for dissolved solids and other nasties that will collect over time in the tanks.

It is your personal choice but I would not recommend changing less than 30% a week reagrdless of bioload. Some say it is a waste of water but my house plants and roses need to have water also so it is an easy source of water that already has some nutrients in it even if you don't dose ferts for plants.
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post #4 of 7 Old 01-29-2007, 02:28 PM
Re: Water Change Frequency 40gal / 15 fish < 1" each

Originally Posted by Us5Camp
... So, how often should I be doing water changes? with or without gravel vacuuming? ...
F4A has way more experience than me but several items:

1) My tap water is very poor for plants and to some respect for fish. In addition the characteristics of the tap water vary depending upon which surface reservoir (there are 5) is being utilized for raw water.
I have a wet/dry filtration system.
In order to overcome the poor and variable tap water situation I have RO water plumbed into the sump of the filtration system.

2) I do 25% to 30% weekly water changes with RO water.

3) I do monthly bottom vacuuming with a Python.

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post #5 of 7 Old 01-29-2007, 03:29 PM Thread Starter
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Re: Water Change Frequency 40gal / 15 fish < 1" each

Originally Posted by jones57742

1) My tap water is very poor for plants and to some respect for fish. .....
Exactly... I assumed (perhaps erroneously) that water changes as frequent as 1/week would introduce more 'shock' than a longer period, say 2-3 weeks.

Maybe I am all wet?...

Thanks for the feedback. Others? Your practices / experiences?
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post #6 of 7 Old 01-29-2007, 03:31 PM
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Personally I prefer to stick to smaller water changes but much more frequently. I change out roughly 10-15% of my water in my main tank almost everyday...longest gap between changes is every other day.
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post #7 of 7 Old 01-29-2007, 05:32 PM
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Jones hit it right. I always forget to talk about tap water conditions because my tap water is almost completely clean and the parameters are all 0 and pH is 7.0. The only thing it has in it is PO4 and that is less than .5ppm. His schedule is more than adequate for most tanks as long as you watch the fish for a while to make sure they adjust. I am so glad I don't have to deal with RO. It can however make a lot of difference in changes needed because of the purity.

Overall the 50% recommendation is simply for this reason: When you change out 50% you should never have to worry about anything being at levels that should hurt your fish. I hate testing and I can't read the things anyway so testing for me is a pain and causes more problems than solutions. Therefore I change 50%. Now if I had a couple 55 gallons a 75 and a 125, you can bet I would get a better test kit and a better way to tell my exact levels because I surely would not want to change 155 gallons of water a week with or without a python.
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