use rainwater instead of tap water

[Catfish Joe]

Hi is it possible to use rainwater instead of tap water for the fish tank.
I have a nine thousand liter tank and a 1.2 thousand rainwater tank.
Rain is collected of a 20 cement tile roof, currently only used for my orchids.
Many thanks in advance

[Aeonflame]

WOW. That tank is massive... upwards of 2000 gallons. What fish do you keep?

If you live in or near a heavily urbanized area, there could be toxins from pollution dissolved in the water. Apart from this, you would need to check your water chemistry to make sure it is suitable for the fish you want to keep. Especially since it is collected from a cement roof.

[jeffs99dime]

What Aeonflame said plus you would have to constantly monitor your source water because it would be changing all the time with no way to regulate the various parameters. Is this going to be an outdoor tank like a pond or something?

[Orion5]

I knew someone who used to use rainwater from an un-treated tile roof, and it worked out well. But as mentioned in other posts, if you're in an urban area this could cause a problem. My buddy was in the country, and still filtered the water through activated carbon for a few days before using it. He didn't test it for anything beforehand, but I imagine that was wreckless... you should if you can.

I would totally try it. :)

[Zander]

As was said before the main thing to keep in mind is the surface it is draining off of.

Rain water is also going to be extremely soft. You didn't mention what types of fish you have but that may or may not be what you want. I know a good number of people use rain water for water changes. Specifically people who keep fish that prefer low PH like Apistogramma.

[Lady Hobbs]

I collected rain water once and was surprised how dirty it was. Smoke stacks, fireplaces, planes spraying for insects, etc. I wouldn't use it.

[steeler58]

Zander makes a very good point about the softness of rainwater. The old timers used to collect it to breed fish like Discus and tetras so not all fish will thrive in it.

Everybody else that mentioned living in an urban setting is right about the water quality for the reasons Lady Hobbs pointed out.

[jeffs99dime]

As I stated earlier, your source water (rain water) would have different levels all the time. What filtration would you use?

[ddavis1979]

I will need to a see a picture of a tank that awesome!

Rainwater is unpredictable. The softness can weaken the shell of some invertebrates. Also pollutants from the air are not easily tested and can kill some fish. However, it is more natural than your tap water for sure.

Its very risky, but as long as you are comfortable with the risk, it can be a good learning experience.

[Catfish Joe]

I will need to a see a picture of a tank that awesome!

Rainwater is unpredictable. The softness can weaken the shell of some invertebrates. Also pollutants from the air are not easily tested and can kill some fish. However, it is more natural than your tap water for sure.

Its very risky, but as long as you are comfortable with the risk, it can be a good learning experience.

Thanks all for the comments, yes it is close to several villages around the area.
I have tested it and PH often around 5.
Was just a thought, my fish tank is a small one of 90 liters.
i will stick to the town water, it comes from a river pumped into a huge holding dam. in times of drought it is pumped from bores spread over a large area.
Thanks