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i've read about ten books on fish and have been to many web site and when it comes to water changes everyone has a diffrent annswer from once a week, twice a week and once a month. so im asking the questine how often do you change your water? i do mine once a week to stay on the safe side.

It depends on your aquarium and its fish. I do my terrapin's aquairum once a week at 35% and try to do my smaller 33 gallon twice a week and aim for about 35-40% a week in total (2 buckets on the weekend and a bucket in the middle of the week). Those fish in the smaller tank only eat frozen food and that always goes everywhere.

I think it's basically easy. You should at first measure nitrites in your tank and find out, how long they will remain under 0,20 mg/l. Provided your filter is not choked and you don't wash your filter mop in hot water (which would kill nitrification bacteria), poisonous ammonia and nitrites (NO2) will be permanently converted to nitrates (NO3) that are the source of nutrients for plants and are not harmful to fish (they are harmful at some concentration, but it's only rarely achievable in aquarium).

Nitrification bacteria usually need some time (about 2 weeks) to settle in the filter mop, so if you set up a new tank, you will probably observe that NO2 increase during the first weeks. But if nitrification bacteria start to work, the number of fish is relatively small and you have enough plants in the tank, then the concentration of NO2 will suddenly start to decrease over time and such a biological system in aquarium may work for many months. From this you can deduce that it's not wise to place too many fish in a new tank, because the little number of bacteria can't work their waste. If NO2 remains high even after many weeks or months, then you may have too many fish in the tank (and too little mop with too little bacteria in your filter).

But naturally, aquarium is a closed system, so after some time the volume of waste may be too big even for a big filter and if NO2 start to increase, you must change water. If plants are not able to consume all the NO3, then even NO3 will increase and as a result, plants will usually die. As I said, the high concentration of NO3 is not dangerous to fish, even if it is around 100 mg/l (in fact, the lethal level - at least for European fish - is about 1000 mg/l; tropical fish may be much more delicate, but still, those tradesmen, who say that if it is 50 mg/l, you must immediately buy their anti-nitrate chemicals, strongly exaggerate, at least). But if nitrification bacteria die from some reason, then nitrates can be quickly converted to NO2 and you have a big disaster in your tank.

I myself have never paid attention to it, but recent changes of the quality of my tap water forced me to buy a set of chemicals and I started to observe the chemical changes in my tanks. Frankly, I was shocked, because it was very different from what I supposed!

And as for waterchanges, I rather prefer big changes of water after a long time. I think that it may not be ideal in a community tank with a lot of plants that may suffer from too much fresh water (not speaking about fish, but it depends on what your water is), but it's certainly better in breeding or rearing tanks, because after some time the water is full of bacteria that multiply from uneaten food, and they can massly kill young fish.

I have a range of different sized tanks and I go by the bigger the more stable so my regime is as follows

400l once a week 25%
120l twice a week 20 %
95 l every two days 10%
50 l breeding tanks every day 10% unless cycling for season mimicing.

I wont mention the egg and fry tanks which are 50% twice daily ( dont you just love fish keeping )

Hope this helps

i do 50% once a week in each tank

cartouche wrote:You should at first measure nitrites in your tank and find out, how long they will remain under 0,20 mg/l

Nitrites should always read 0, PERIOD.
I do 20% weekly water changes on most tanks, depending on the population, and 20% to 40% daily w/c on my grow up tanks.

On the principle I agree with Cartouche, although I also agree with RiC that on an established tank, Nitrites should be zero...

But I would also like to add that keeping the nitrates as low as possible, and under 50 mg/l (ppm) would be preferrable, for the health and growth of the fish - and nitrate levels should really be the guiding factor for how often you do water changes. Unless you have some filter that removes nitrate, in which case that's not a good measure...

My tanks tend to get 30-40% water changes once a week - I don't test the nitrate levels, because:
A. The supplies from Thames Water is high in nitrate, so I'm not going to get it particularly low...
B. It's not going to HURT if the nitrate levels are LOWER than whatever limit you set.

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Mats

My tap water has 40 mg NO3/L at the moment, so keeping the nitrates down is not a meaningful issue in me. I must live with it

If you measure nitrites, say, twice a week, then a level of 0,10 mg/L is acceptable and safe, too. Naturally, it's better when they are 0,00. Some fish may also be more sensitive to NO2 rhan others and if you have an established tank with fish, they may adapt to higher NO2 levels over time. Yet if you buy new fish and give them into the tank...

I don't agree that some level of nitrite is acceptable. That means that somehow your biological filtration (nitogen cycle) isn't working as it should - either because you have too much stock in the tank, or because the the bacteria have died or something like that...

Obviously 0.1 ppm isn't as bad as 0.5 or 1ppm (or 10 ppm, as I've seen in one post of someone who had just A FEW too many big fish in a newly set up tank!]

Edit: Of course, some small amount of nitrite will be in the tank if you have living creatures/plants in the tank. However, if the test-kit for aquarium testing can measure it as above the first step of the scale, then it's too high!

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Mats

I change the water at least once a week in the tanks. But, how much water I change depends on what species are in the tank. If there are juveniles(fry), they require small water changes daily(as small as a 1/2 gallon, depending on how much water is in their tank). Some species, like Chaetostoma sp. like very clean water and may require a second small water change during the week. The 75 gallon tank usually gets a 20-25% change once a week. The same with the 29 gallon tank. These are community-type tanks. Each tank is an entity (or ecosystem) unto itself. It's up to you to test, and retest the water to make sure everything is okay. I try to think of it this way: I'm cleaning their toilets(the tanks). They live where they do their "business." How would I like to live in that?
Amanda

My overstocked 300l tank gets almost a 50% change... thrice a week! Nitrates tend to go up by about 5ppm a day in that tank so I have to stay on it. The water changes are such a routine now that the Brochis cats all go line up at the front as soon as it starts because they know I will bury some live or frozen worms in the gravel for them to dig out

Some of my tanks get weekly water changes no matter what, 50% or more, rarely any less. Sometimes I slack off and a couple tanks go a few days longer then I like or a couple weeks between changes but these are the ones with less fish.

Lately, my African c***lid mbuna tank gets about 25% every week. My discus tank gets 25% about 3 times per week, nto to mention filter changes and glass wipe-downs more often. My 40 gallon pleco tank full of fry gets about 10-15% almost every day due to the waste from the zuchini and melon and the fact I am trying to get food to them. I have another understocked pleco tank that gets about 20% twice a week. I have a pair of angelfish in a 25 gallon that gets a vacuum of the bare-bottom almost every day, and then topped off. I guess that is about 10% daily.

I keep a bunch of tanks, so I change 40 percent of the water in the freshwater tanks all day Saturday and 40 percent of the water in the marine reef tanks all day Sunday. Those with sumps are easier as I drain the sump and refill it with new water. Takes about 10 minutes.

Dave

djw66 wrote:I keep a bunch of tanks, so I change 40 percent of the water in the freshwater tanks all day Saturday and 40 percent of the water in the marine reef tanks all day Sunday. Those with sumps are easier as I drain the sump and refill it with new water. Takes about 10 minutes.

Dave

Nice to hear from you, Dave! Are sumps that much easier to change? I would imagine it disturbs the tank less too, but do you have to vaccuum the substrates(if there are any)?
Amanda

I wont mention the egg and fry tanks which are 50% twice daily ( dont you just love fish keeping )

The fellow at my LFS told me thats its no good to change your water every day, but could not give me a reason. so now i have conflicting oppinons. who's right? i dont mean to insult anybody im just trying to get to the bottem of this

Frequent water changes can be stressfull to sensitive fish (easily stressed/nervous disposition types that is).

Also, if you don't make sure that the water parameters (pH, Temp, and such) are very similar, some fish may very well be disturbed by the variation. Lake-living species are more likely to be affected by sudden changes than those living in rivers (as rivers are often naturally varying between dry-season and rainy-season, and those changes can be quite sudden - when the rainy season starts, you can have a sudden, large flood of fresh water come into a stagnant section of the river - and species that don't survive this would have naturally eolved away).

But in general, frequent water changes isn't going to be a problem to most species.

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Mats

Hiya 'Manda,

Thanks for the welcome, I've been advising novices on another forum on basic aquarium keeping for a while (Amazing no one reads a book anymore . . .), and recently recovered from a Brown Recluse spider bite on my arm.

Yep, a sump is easier to isolate and drain than the main tank, at least for me, as most of my sumps are close to 50 percent the size of the main tanks they reside under. I close the gate valves, turn off the power strips, and drop in a mag drive pump with about six feet of silicone tubing (seems to last longer for me) attached to the outflow. The height of the pump leaves a couple inches of water in the sump so it doesn't leave the critters present high and dry. I use a smaller pump to refill the sumps with fresh water, of course of the same temps and chemistry.

Turn on the power strips, open the gate valves, and I'm done. Takes about 10 minutes.

As far as vacuuming, I do so once or twice a month were there's exposed gravel. As my freshwater tanks are pretty heavily planted, I can't vacuum those areas, so a couple times a year I take a power head and run it around the planted areas to get the accumilated goop up in suspension to be removed by the prefilters or canister filters or both. Dosen't seem to bother the fish a whole lot when I do that. Guess they think its a storm of some type.

Dave

kdawg wrote:I wont mention the egg and fry tanks which are 50% twice daily ( dont you just love fish keeping )

The fellow at my LFS told me thats its no good to change your water every day, but could not give me a reason. so now i have conflicting oppinons. who's right? i dont mean to insult anybody im just trying to get to the bottem of this

They can never give you a reason. The reason to change water two or three times a day in egg & fry tanks as that, plus space, plus proper foods, gives you considerabley larger, healthier fry and higher yields.

Its well known that if you do the above, the fish you raise will be a good deal larger and healthier than anything you can find in stores.

Dave

I do a 30% water change once a week using rain water as this gives my tanks perfect readings on all Nitrates, Nitrites, Ph and everythig else.

the discus breeders in asia amaze me, they can do 3-4 water changes a day whenever they please cause they have the warm, dechlorinated water on tap, lucky people! the discus breeder i got mine off does up to 80% twice daily on some of his grow out tanks hes got the powerhead and aging barrels (10 200L bins) set up so its not as much work compared to the old bucket method

two of my tanks get weekly 50%, two get daily 30% another gets 30% every 2 days

kdawg,
Frequent changes in a fry tank are important because you're keeping all the food particles from amassing. The fry grow quickly and as they grow, they will put out more and more waste. It's important for you to keep up with those water changes. Some folks may think you need to "age" the water, or the worry of losing all the "good" bacteria. To avoid this, I don't change water and filter media on the same day. I do one or the other.

Here's how I dealt with the confusion: I noticed everybody has a different way of changing water. But, a lot of people have nice looking tanks. What are those people with the nice looking tanks doing? I borrow a little of this and a little of that and work it into the tanks that I have with the species that I have. It takes some thinking and some research, but it's worth it! The Cat-eLog on this website is excellent for telling you which catfish species like what kind of water, etc.
Amanda

if you did like two 50% water changes daily could you get away with not useing a filter?

No, you still need the filter to help circulate water past the bacteria that take care of the ammonia to nitrate conversion.

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Mats