water changes...how often

Dunluce2 said:

Do you experienced people water change weekly, fortnightly, monthly or at a particular nitrate or nitrite level.

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Yes - except, a cycled tank should have 0 nitrites.

Pick a schedule that works for you knowing that more often is better - weekly usually works for that. First, get your nitrAte to a level that’s good (e.g. under 20 ppm or under 10). In one week, take another reading. Say it’s now 40 ppm. Now you can find out what % of water you need to change to get it back down to your target. See if that’s consistent week to week. Once you have a pattern, you can stop testing so often – just once in a while to see if your your % is still working with your target reading. There are a lot of other pollutants you are getting out with water changes, but nitrates are easy to monitor.

Another consideration is if your tank is planted or not, because that will affect the nitrate readings.

60 litres = 15.85 US gallons. I would say it is quite overstocked. Also, that tank is not big enough for an angel fish.

The 40 L isn’t too bad.

In books and magazines, I've most often seen 10-25% weekly preached, and have occasionally seen 25% once a month quoted.

I, however, think the best answer is to use a nitrate test kit and test your water before and after every change to see if you're keeping it at a safe level until you've established what your water change requirements are. I wait a few hours after I've performed my weekly water change to let the water mix well. If your nitrates are climbing beyond a safe range, you will need to increase the amount or frequency of your water changes. If they're remaining fairly constant, and in a safe range, you're probably doing OK.

The test kits I have and recent magazine articles I've read say that you want below 40-50 ppm nitrates in a freshwater tank (and quite a bit lower for marine tanks), although I see that many people here like to keep below 20.

I change about 13% every week in a community tank, and my nitrates remain in the 5-10 ppm range.

I do 30-40% Weekly. Exsesive? Maybe, but IMO It's the best way to head off problems like disease, and algae. In your case (overstocked 15g) 50% weekly would be my recomendation. I really don't think 10% water changes are very usefull at all. Why would you go through all the trouble of getting out the buckets and siphon just to take you nitrates (and other tank pollutants) from 40ppm to 36ppm?

My fear of going much over 25% at one time except in an extreme emergency is the shock to the fish by the change in water chemistry.

As long as you are using the same water source, and get the temp. within a degree or two, there shouldn't BE a large change in the water chemistry. The exception is that sometimes ph can change when it sits for a while. Simply test your tank water, and your tap water and see if that is the case.

There is really no set RULE for water changes. Overstocked (in the case of your first tank) need larger water changes to keep things clean. There are many things that build up in a fish tank that we can't test for. IMO for a normally stocked, filtered tank, at least 20-25% a week is a good rule, but some do much more than that, and their fish probably thank them :dance:

As long as you're doing the larger changes frequently, there should be very little difference in water chemistry. There simply isn't enough time between changes for shifts in chem to occur. People who are growing out fry, keeping discus, and stingrays often do 50% or larger daily!

That is why I always advocate more frequent changes. Some people do 50% once a month. that's when I would worry about changes in chemisty between tank and tap.

Breeders commonly do 100% or more daily.

I do 1/3 to 1/2 weekly, and that lower number is on severely understocked tanks (none of my tanks are overstocked - I am too conservative for that)

On my 10 gallon puffer (1 - F8) I change 25% about once every 2-3 weeks.
72 gallon community I change 15-20 gallons every three weeks.