Introducing rainwater into water changes

[Suthypie]

Hello,

As you’ve read; I’m now keen to take the shift into introducing rainwater into my water changes for my 200l freshwater planted tank. I live in a very hard water area. The GH (20) and KH (16) are way over the comfortable limit.

Would greatly appreciate any feedback on my plan here:

- collect rainwater in a separate water butt (not one that drains of a roof or any other contaminated surface)
- once collected. Boil that water to remove any contaminants that may have developed while sitting there.
- once at desired temperature. I will mix this with pre-treated tap water to do my water changes.

Obviously I have to be mindful and play around with the amounts as to not alter the ph too much. But just looking for some guidance on whether this approach is suitable.

Thanks All

 

[Byron]

The combining of the two types of water will obviously result in a different GH, KH and pH. So the first thing is to know these numbers for both water types. Rainwater should be zero GH/KH, and probably (given the atmospheric CO2) pH on the acidic side. Mix half rainwater and half tap water, and test these three parameters. Assuming the GH/KH to be zero. the GH/KH of the mixed waters will be proportional, i.e., if half rain and half tap, the GH/KH should be half what the tap numbers now are. The pH will depend upon the two waters pH, but pH is influenced by several things including the CO2, GH and KH, so it will need to be measured as it will not be "half" or whatever.

 

[Lynnzer]

I did a full topic on this sort of thing. I use water that runs off my kitchen roof though, albeit the area is relatively free of airborne nasty chemical stuff.
I made a filter to fit in the rianwater downpipe, including a pouch of activated charcoal to help take ot any microbacteria. The filter itself is great for collecting the bits of moss and dust from the roof so what eventually gets into the barrel is as safe as I can make it up to a point.
I'm awaiting delivery of a 7K UV light so that each time it rains and the barrel has new water, I will switch the light on for a couple of hours.
When the barrel is full, ie 100ltr, I fill 5litre bottles from the barrel and store them in my garage as you never know when it'll next rain.
Yesterday I changed 40% of my two aquascaped tanks totalling 65ltrs.
I find the best way to get the temperature right is to put the 5ltr bottles in a bath of hot water and keep checking the bottled water. It works like a dream for me.
I didn't have to mix the water yesterday as I'm reducing the GH and taking out salt water that I added for a minor infection problem, however I keep notes on the parameters of my tapwater which has become suddenly a lot better than it was only a week ago, also the bottled water and the rainwater which is virtually at zero on all counts. I have a chart made up to say what mix I need from all sources to achieve what I need for each of my 7 tanks as they are all different.
If you search the forum you'll find the topic if you want better instructions on making a filter for a pipe etc.

 

[Colin_T]

What sort of fish are you keeping?

 

[Suthypie]

What sort of fish are you keeping?

Black skirt tetras, Cory’s, a bristlenose catfish, and keyhole cichlids

 

[Suthypie]

The combining of the two types of water will obviously result in a different GH, KH and pH. So the first thing is to know these numbers for both water types. Rainwater should be zero GH/KH, and probably (given the atmospheric CO2) pH on the acidic side. Mix half rainwater and half tap water, and test these three parameters. Assuming the GH/KH to be zero. the GH/KH of the mixed waters will be proportional, i.e., if half rain and half tap, the GH/KH should be half what the tap numbers now are. The pH will depend upon the two waters pH, but pH is influenced by several things including the CO2, GH and KH, so it will need to be measured as it will not be "half" or whatever.

Thanks for explaining so clearly. I’ll test the parameters and find a good level for what I need.

 

[Suthypie]

I did a full topic on this sort of thing. I use water that runs off my kitchen roof though, albeit the area is relatively free of airborne nasty chemical stuff.
I made a filter to fit in the rianwater downpipe, including a pouch of activated charcoal to help take ot any microbacteria. The filter itself is great for collecting the bits of moss and dust from the roof so what eventually gets into the barrel is as safe as I can make it up to a point.
I'm awaiting delivery of a 7K UV light so that each time it rains and the barrel has new water, I will switch the light on for a couple of hours.
When the barrel is full, ie 100ltr, I fill 5litre bottles from the barrel and store them in my garage as you never know when it'll next rain.
Yesterday I changed 40% of my two aquascaped tanks totalling 65ltrs.
I find the best way to get the temperature right is to put the 5ltr bottles in a bath of hot water and keep checking the bottled water. It works like a dream for me.
I didn't have to mix the water yesterday as I'm reducing the GH and taking out salt water that I added for a minor infection problem, however I keep notes on the parameters of my tapwater which has become suddenly a lot better than it was only a week ago, also the bottled water and the rainwater which is virtually at zero on all counts. I have a chart made up to say what mix I need from all sources to achieve what I need for each of my 7 tanks as they are all different.
If you search the forum you'll find the topic if you want better instructions on making a filter for a pipe etc.

This is great! I didn’t think about storing the extra amounts in bottles in the garage. I’ll be sure to check out the diy filter too. Thank you!

 

[Colin_T]

You want the GH below 150ppm for these fish and if possible around or below 100pm.

Your current GH is around 360ppm so if you use 2 parts rain water to 1 part tap water, you would get a GH around 120ppm.

If you use 3 parts rain water and 1 part tap water, you should get a GH around 90ppm.

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I would go for 120ppm and make the water up and aerate it for 30 minutes or so before using it. Then do a 10% water change each day for a couple of weeks. This will slowly bring the GH and pH down. When the water in the aquarium has a GH around 150ppm, you can do bigger water changes.