What is the best for my goldfishes?
I can choose between 2 types of water.
- Rain water that is collected in 2 big underground tanks and has different pipelines (to flush the toilet, water the plants,..)
- The water that we use (to drink, cook etc) is water that passes trough a filter to minimize the Chlore and other stuff.

Or should I use a mixture of the above?

I started with rain water because I rescued them from a very smal dirty pond and I didn't wanted to give them a shock. The firt week I changed 50% of the water with de filtered water.

I really hope that I didn't do anything wrong. I my goldfishes.
My boyfriend is already complaining that I give the fish more affection then I give him.

can you get the water params of both the rain water and the water that you use

hi Quasi and

rain water is not the most ideal water for goldfish as it is extremely soft and is better suited to tropical fish such as tetras. Goldfish like the harder alkaline water that is usually has a ph around 6.8 - 8.2 that is the ideal ph range for goldfish where as the ph of rain water is usually around 6.0 - 6.6. The water which you drink is most likely the better choice. is it straight from the tap or does it come through a filter? if it passes through a filter to remove chlorine and chloramine then it may also remove the minerals from the water which goldfish and all other fish thrive on.

If it is only being treated for chlorine and chloramine then that is no problem you could either use that or straight from the tap and treat with a water conditioner such as a amquel, amquel plus, stress zyme and prime prime being the best out of all of them. Most people on this site use prime but they all of those water conditioners do the same job. Prime has the advantage as it binds ammonia in the water to make it less toxic to your fish, no water conditioner on the market removes ammonia but there are products spefically designed to remove ammonia. They are very inneficiant and all you are really buying is an expensive bottle of liquid. also you should check the water params of the rain and tap water and decide which is better for goldfish. You should check them for all ph, ammonia, nitrite, nitrate and if you have test kit gh and kh

Thanks for the explanation.

The filter only removes the chlorine and chloramine.
I've tested the water of the filtered tab, and the nitrates are 20 ppm.
The rain water indeed had a lower pH. I've done an other change of water (with the filtered tab water) and the values are now all right for the fishes . Only nitrate showed in the water.

i would use the tap water the disadvantage is that you don't want nitrate over 40ppm so by having it at 20ppm then you really do not have much to work with, i would still use it though. it is better than my tap water which has 1ppm of ammonia in it