Water change interval

[cyakka]

I have received differing advice regarding water changes during aquarium nitrogen cycling. I have set up a new 90lt tank with 4 Glowlight Tetras providing the ammonia. I have put in a few live plants and have been using Cycle and Aquaplus as directed.

This is day 4 and I am planning to do a 20% water change on day 7. Then weekly changes for the 1st month.

Am I doing this correctly?

[hovmoller]

Yes you are :thup:

[blueether]

and after the first mont each week as well...

[cyakka]

Thank you both for your help

[blueether]

Thank you both for your help

now that you are doing weekly water changes... It all depends on the stocking rate, and maybe how heavy planted it.

To give you an idea, in my 430 L native tank I have to do a 30% or more water change every week to 10 days but in the 160 L and 60 L planted tropical I can get by with 30% changes about every 2 or 3 weeks.

[Ira]

I just do weekly* 50% water changes because half is a nice easy number.

*Ok, I've been lazy for the last few years and it's every 3-4 weeks.

[blueether]

I just do weekly* 50% water changes because half is a nice easy number.

*Ok, I've been lazy for the last few years and it's every 3-4 weeks.

When I say 30% I really mean I stick the siphon in and start it, when I remember or I hear the wavemaker sucking air I take it out and re-fill.

[Ira]

When I say 30% I really mean I stick the siphon in and start it, when I remember or I hear the wavemaker sucking air I take it out and re-fill.

The "Awdamnit now I have to reprime my filter" method. I use that frequently too.

[blondfish]

You should be doing water changes every time you see ammonia/nitrite during the cycle.

After that 20-50% weekly is a good amount.

[calculator]

Again it depends on your stocking, just watch your nitrates and fish helth for how often you need to water change, I over stock slightly (ok I over stock quite a bit) and do a 50% once a week, and 30% once or twice a week as well.

[F15hguy]

as you can see the advise is differing because there is no proper answer. I recomend a minimum of 20-30% per fortnight, preferably weekly with the additional if I have time i'll do one.

some times I'll do 4-5 in a week, sometimes just one.

small tanks need a lot more than big ones, and stocking levels also affect it.

there is no negatives for doing a water change and heaps of positives. (unless you have major water temp or pH imbalances)

the real question is how few a number of water changes can you get away with without problems?? and is it worth risking your babies to save yourself 1/2 an hour a week?

[Phantom]

I don't do them as often as others say here, but I do have larger tanks, lighter stocking, have plants and use purigen.

My rule of thumb is to keep an eye on nitrates. 40ppm is the absolute maximum I would ever let them go to. Once I know how fast they build up, I do 50% water changes at an interval that won't allow them to build up that high.

[F15hguy]

lol 40ppm is the MAV for humans, would hate to have to be a fish in that.

at 50ppm human babies start to get Blue baby syndrome, and thats just drinking it, not existing in it.

I say 20ppm is a maximum

[Phantom]

Really? I've always gone on 40 as being the max safe level. I generally change earlier than that though.

I was also of the understanding that many places in NZ have tap water that has at least 20ppm nitrates in it.

[F15hguy]

I would be surprised at that for tap water, unless it is bore water.

the 40ppm thing is put out there by the industry. just seems strange that for "sensitive fish" they say maximum 20ppm.

just cuz a fish can handle a level doesn't mean that it is good for it.

[Caryl]

40ppm is often our tap water.

[F15hguy]

"High levels of nitrate can pose a health risk for certain people. For this reason the

Drinking Water Standards for New Zealand set a Maximum Acceptable Level (MAV)

of 11.3mg/L for nitrate

-

nitrogen. This level is based on international standards."

thats from http://www.cph.co.nz/Files/DrinkWaterFAQNitrates.pdf

these are the Long-term values, short term is allowable up to 50ppm, but to be serious, I got those readings just downstream of an unlined septic tank sludge settlement pond in a high intensity farming area.

if your getting that sort of levels I would be complaining NOW

(BTW as soon as my marks come back im officially qualified in Water treatment and management )

[blondfish]

I'm pretty sure that the "less sensitive" fish can handle up to 100ppm of nitrates.

It doesn't mean they should be made to though. Its best to keep nitrates as low as you can though.

[F15hguy]

handle?, an old fella in Greerton who keeps his nitrates below 10ppm religiously has a 5 year old neon (possibly 8years, he only bought them twice)

"handle" is a bit relative

[Phantom]

All I was trying to say is you can learn how fast your tank builds up nitrates. Pick an absolute maximum level and see how long it takes for them to build up. That would define your absolute maximum interval between changes.

Remember, if your tap water has 0ppm nitrates and you change at the very latest when it's up to 20ppm, a 50% change would leave you with 10ppm nitrates.

It is best to do water changes as often as practical though, but it doesn't have to be religiously once a week etc if your tank doesn't build up nitrates that quickly. The smaller the tank, the more often you'll have to do changes as parameters can change quicker. Same goes for increasing bio load. Having plants in the tank may reduce the nitrates and extend this timeframe.

I have found that many people I know got out of fish keeping because they were told they have to do water changes once or twice a week and they found it too much effort. I tend to advise people that they need to learn how their system runs and ensure that they do what they can when they can, but don't stress if they miss a week if they know their tank can handle it.

[F15hguy]

:gpo2:

well said.

[alanmin4304]

There is a lot of debate over methemoglobinemia in babies and it is very rare in NZ. There has to be a lot of predispositions as well as nitrate for it to be a problem. My understanding is that it is nitrite that is the problem so baby requires the correct micro organisms to produce that from nitrate. So called healthy foods such as spinach are high in nitrate, and foods like ham and bacon are high in nitrite.