Rain Water for Fish Tanks

[Cohenjl13]

So I have a white 55 gallon drum I want to scrub clean and put a fine net over so it can collect rain water but not to many leaves or bugs hopefully. The plan is to have a pump in the bottom of it running to make sure stuff doesn’t grow in the stagnant water that would have a hose that I will run to my fish tanks to use to do water changes.

Suggestions? Issues? Never done this before or researched it so I don’t know what issues I might run into.

A second thought was to not have the pump running often and seed it with daphnia so when I do weekly water changes it adds yummy food as well.

 

[rlederer]

Make sure you test the rain water. If it runs off a roof it could collect contaminants. (If rain is not running off something but directly into the barrel, it would take a long time to fill. ) Should be soft water, though.

 

[ZxC]

There will be no carbonates in the rain water, so expect a pH crash. No Ca or Mg either, so fish / plants will likely need to adapt to a lower TDS and lower general hardness.

 

[Caliban07]

There will be no carbonates in the rain water, so expect a pH crash. No Ca or Mg either, so fish / plants will likely need to adapt to a lower TDS and lower general hardness.

Incorrect. It depends where you live and a ph crash is unlikely.

 

[Caliban07]

So I have a white 55 gallon drum I want to scrub clean and put a fine net over so it can collect rain water but not to many leaves or bugs hopefully. The plan is to have a pump in the bottom of it running to make sure stuff doesn’t grow in the stagnant water that would have a hose that I will run to my fish tanks to use to do water changes.

Suggestions? Issues? Never done this before or researched it so I don’t know what issues I might run into.

A second thought was to not have the pump running often and seed it with daphnia so when I do weekly water changes it adds yummy food as well.

Don’t put daphnia in the water. Allow them to grow naturally. If you can grow daphnia or similar then this is better than any information a test kit will provide. If the water is suitable for daphnia it’s suitable for your tank. Rainwater is far far superior to the stuff that comes out of your tap.

 

[ZxC]

Incorrect. It depends where you live and a ph crash is unlikely.

And where would the Ca, Mg and carbonates be coming from in rainwater?

https://www.practicalfishkeeping.co.uk/fishkeeping-answers/articles/is-rainwater-safer-than-tapwater

Good read

 

[Caliban07]

Don’t link other misinformed forums please. Rainwater travels through the air before it hits the ground. If you live near areas of limestone geology the rain can pick up Ca and bicarbonate ions from dust. If you live near the seaside traces of Na etc.

 

[ZxC]

Don’t link other misinformed forums please. Rainwater travels through the air before it hits the ground. If you live near areas of limestone geology the rain can pick up Ca and bicarbonate ions from dust. If you live near the seaside traces of Na etc.

They are certainly not misinformed. Rain water contains (usually) less than 10 ppm of TDS, no where near enough minerals for proper fish / plant / tank health. A pH crash is very likely once the buffering ability of the tank has been lost (caused by constant use of pure rain or RO or distilled water stripping the rocks / substrate of their buffering ability, if they have any at all.)

Low carbonate hardness will result in wild pH swings both up and down, far from a stable environment we should all strive for.

My tank requires around 125ppm or more of TDS to give me a decent starting point for kH, gH and pH. 10 x higher than what is found in rainwater, plus I know what I'm putting in the water. Who knows what is dissolved into rainwater....

I'm not saying rainwater can't be used, it is just variable and needs to be boosted with minerals and carbonates to be suitable for decent success "in most if not all cases".

 

[Caliban07]

Me to scientist: Hi ****.

Typically, what is in rainwater? Where you live, is it likely to contain nutrients? Micros etc?

Thanks

Craig

Scientist: Hi Craig,
It depends a little bit where you live, but it may contain traces of sodium (Na) if you live near the seaside, a small amount of hardness if you live where it is limestone geology and a trace of nitrogen if you live near a major conurbation (from exhausts etc) or close to an intensive pig or poultry farm.

It is unlikely to contain any phosphorus because the phosphorus cycle doesn't have an aerial phase. If you live somewhere where it rains a lot and has hard rock (Wales, Cumbria etc) you pretty much get DI water.

My rain-water (Corsham, E of Bath) is about 30 microS in the winter and up to ~150 microS in the summer. Most of the ions will be Ca++ and HCO3- ions from dust.

cheers

 

[Cohenjl13]

Ok calm down everyone. Thanks for all the advice, I’m going to go ahead and research some myself and if I go through with the process I will let you know how it goes!

 

[ZxC]

Ok calm down everyone. Thanks for all the advice, I’m going to go ahead and research some myself and if I go through with the process I will let you know how it goes!

Collect some and post your values. I'm going to test my rainwater today.

 

[Caliban07]

Collect some and post your values. I'm going to test my rainwater today.

What with? [emoji23]

 

[Caliban07]

Ok calm down everyone. Thanks for all the advice, I’m going to go ahead and research some myself and if I go through with the process I will let you know how it goes!

I’m calm. Just have to set the record straight as people search forums like this for accurate information.

 

[ZxC]

I’m calm. Just have to set the record straight as people search forums like this for accurate information.

**** relies on one "scientists" opinion lol, claims it to be 100% accurate and slams other members opinions.

Test my rain water with a calibrated pH pen, TDS meter and cross reference with kH / gH / pH liquid tests? not a hard concept to do in our little fish keeping hobby.

 

[V227]

Based on their threads & Posts, I consider both Z×C and Calibano advanced regarding fish keeping and water management issues. I greatly respect their advice and opinions.
On this issue logic dictates that on average rain water is going to be softer than the waters of lakes and streams. In some industrial regions, the rain water is likely to be slightly acidic as well. In regions where dust and debris are prevalent in the upper stratusphere it stands to reason that the developing rain drops would pick up tiny grains of minerals. The resulting increase in hardness would likely not be enough to be an effective buffering agent.
I'm definitely not a scientist, Lol, just a "Jack of all trades" Fish keeper.
IMO, unless the aquarium is small and the rain barrel is large, collecting enough rain water to conduct the required weekly water maintenence is unlikely, and more importantly unnecessary.

 

[Caliban07]

Based on their threads & Posts, I consider both Z×C and Calibano advanced regarding fish keeping and water management issues. I greatly respect their advice and opinions.

On this issue logic dictates that on average rain water is going to be softer than the waters of lakes and streams. In some industrial regions, the rain water is likely to be slightly acidic as well. In regions where dust and debris are prevalent in the upper stratusphere it stands to reason that the developing rain drops would pick up tiny grains of minerals. The resulting increase in hardness would likely not be enough to be an effective buffering agent.

I'm definitely not a scientist, Lol, just a "Jack of all trades" Fish keeper.

IMO, unless the aquarium is small and the rain barrel is large, collecting enough rain water to conduct the required weekly water maintenence is unlikely, and more importantly unnecessary.

I mean it’s just that I’ve been topping up with RO water and done 0 water changes in the past 5 months and haven’t experienced a pH crash or had issues with buffering. My snails are thriving. Of course rainwater will be naturally softer but the issues surrounding this are just a myth. And my argument was the minerals in rainwater will differ depending on your geographical location. Best not to assume it’s all one and the same.

 

[Caliban07]

**** relies on one "scientists" opinion lol, claims it to be 100% accurate and slams other members opinions.



Test my rain water with a calibrated pH pen, TDS meter and cross reference with kH / gH / pH liquid tests? not a hard concept to do in our little fish keeping hobby.

You follow the workings of one of the most flawed ‘scientists’ in the hobby. You have no idea about the accuracy of hobby grade test instruments or how difficult it is to even obtain an accurate reading of most of these ‘essential’ parameters even using £100,000s of lab grade analytical equipment. Your just kidding yourself if you think you can get anything meaningful with those tools. The most accurate tool we have in the hobby is the TDS meter and even it’s very name is flawed and misguided. It doesn’t even measure the total number of dissolved solids [emoji23]

 

[ZxC]

I mean it’s just that I’ve been topping up with RO water and done 0 water changes in the past 5 months and haven’t experienced a pH crash or had issues with buffering. My snails are thriving. Of course rainwater will be naturally softer but the issues surrounding this are just a myth. And my argument was the minerals in rainwater will differ depending on your geographical location. Best not to assume it’s all one and the same.

A 0 water change system is very unique... of course you aren't experiencing my "dreaded pH crash" .... nothing out means nothing in. OP never specified which style tank they will be running, but 99% of successful owners are water change people, assuming OP is referring to using the rainwater for water changes AND top ups is where I was going.

A pH crash won't happen in that tank because you aren't removing anything that needs replaced (minerals, carbonates etc.). You also wouldn't be adding anything and therefore the tank would maintain a "stable" balance. No different than me topping up my tanks with my RO water...

Now, removing all kH from constantly using rainwater for water changes and top ups will result in a very unstable pH, where small changes will result in large pH swings, killing off BB etc.

Heck if I had known you were talking about a 0 water change tank I would have advocated for rainwater for top ups.... despite the likelihood of pollutants in that rainwater, but I'm sticking to OP using rainwater for both water changes and top ups.

 

[Caliban07]

A 0 water change system is very unique... of course you aren't experiencing my "dreaded pH crash" .... nothing out means nothing in. OP never specified which style tank they will be running, but 99% of successful owners are water change people, assuming OP is referring to using the rainwater for water changes AND top ups is where I was going.



A pH crash won't happen in that tank because you aren't removing anything that needs replaced (minerals, carbonates etc.). You also wouldn't be adding anything and therefore the tank would maintain a "stable" balance. No different than me topping up my tanks with my RO water...



Now, removing all kH from constantly using rainwater for water changes and top ups will result in a very unstable pH, where small changes will result in large pH swings, killing off BB etc.



Heck if I had known you were talking about a 0 water change tank I would have advocated for rainwater for top ups.... despite the likelihood of pollutants in that rainwater, but I'm sticking to OP using rainwater for both water changes and top ups.

No I know the op was taking about water changes. Due to some of your comments in the last post I’m out. I really can’t take you seriously anymore.

 

[ZxC]

@Cohenjl13

Yes, rainwater can be used for your tank. But, know that rainwater is not always a reliable source. It's likely to change as the seasons go by throughout the year, in different weather patterns etc.

You will probably want to boost the water a bit, or remineralize.

I recommend (others opinions will be different) the following:

For carbonate hardness (kH) you'll want 2-3 degrees, unless you are looking to keep fish or shrimp that require very soft water. You can achieve this by either mixing the rainwater with your tap water, or boosting the pure rainwater with baking soda NaHCO3. Check out https://rotalabutterfly.com/nutrient-calculator.php# and punch in your water volume and your desired levels. It will tell you how much to dose.

For general hardness (gH) you'll want anything from 4-10 degrees depending on the tank. If there is plants I would recommended 8-10 degrees, if no plants 4-6 degrees. Again, this can be done with a rainwater/tap mix or by using pure rainwater boosted with some Seachem Equilibrium or using CaSO4 and MgSO4.

Top offs can and should be done using pure rainwater so as to not have your overall TDS increase.