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Rain water from gravel roof causing problems?

Sanniejop

Sanniejop

Member
Joined
31 Jan 2022
Messages
51
Location
Netherlands
Hello all,

Our tap water has a KH of 8, so I was thinking to do water changes with 50% tap and 50% rain water to lower the KH. Water change itself is 60L on 185L Total.
So to say, I did this once and promptly I saw a brown layer on my anubiases leaves. My oto's are happy to eat it it seems.
I never saw this brownisch layer before but I guess this will be the famous diatoms?
My question is can this prompt occurence of diatoms be related by the fact that the rain water is coming from a flat roof with gravel on it? Can this gravel cause a higher level of silicates in the rain water?

And then the next question. Is there a simple way to remove these silicates from may rain water?
Thanks in advance,
Sandor
 
Hi all,
Sanniejop said:
My question is can this prompt occurence of diatoms be related by the fact that the rain water is coming from a flat roof with gravel on it? Can this gravel cause a higher level of silicates in the rain water?
Click to expand...
It shouldn't. The quartz (SiO2) in gravel is inert <"Aquarium sand and diatoms...">. You only need the merest trace of orthosilicic acid (Si(OH)4) for diatoms to be able to extract it, diatoms are universal in fresh (and salt) water. In fact they occur everywhere there is liquid water.
Sanniejop said:
And then the next question. Is there a simple way to remove these silicates from may rain water?
Click to expand...
You can use a <"silicate removal resin">, but because rainwater is "distilled" it shouldn't actually contain any silicates and definitely a lot less plant available <"Orthosilicic acid - Wikipedia"> than ground water.

cheers Darrel
 
Hi all,
Sanniejop said:
Our tap water has a KH of 8, so I was thinking to do water changes with 50% tap and 50% rain water to lower the KH. Water change itself is 60L on 185L Total.
Click to expand...
A thought occurs that the softer, less alkaline water may have "unlocked" the availability of one of the other mineral nutrients that was limiting diatom growth?

cheers Darrel
 
Hi Darrel, thanks for your reply.
So they will always be present in the rainwater too? Or maybe there must be a different source for those traces of orthosilicic acid?
I used a second hand rain barrel. There were some old leafs in the rain barrel. Also on the roof there are leafs and mosses present.
I understand amorphous silica can extract from silicon-rich plants?
I have really no knowledge in this area .
 
dw1305 said:
Hi all,

A thought occurs that the softer, less alkaline water may have "unlocked" the availability of one of the other mineral nutrients that was limiting diatom growth?

cheers Darrel
Click to expand...
That is an interesting though. Target was also to reach a lower Ph. Can this also play a role in this way of thinking?
 
I was thinking rain water could do no harm, but I was really surprised by the sudden appearance of those diatoms. I never saw them before.
Maybe at the start of the tank but that was eight years ago.
 
Hi all,
Sanniejop said:
So they will always be present in the rainwater too? Or maybe there must be a different source for those traces of orthosilicic acid?
I used a second hand rain barrel. There were some old leafs in the rain barrel. Also on the roof there are leafs and mosses present.
I understand amorphous silica can extract from silicon-rich plants?
Click to expand...
Unfortunately we are in <"unknown unknowns"> territory. I'm guessing it isn't the rainwater, but it is purely a guess.
Sanniejop said:
Target was also to reach a lower Ph. Can this also play a role in this way of thinking?
Click to expand...
A <"lot of mineral nutrients"> are more available at lower pH and alkalinity values, iron (Fe) is the one <"we often encounter">.
Sanniejop said:
I was thinking rain water could do no harm, but I was really surprised by the sudden appearance of those diatoms.
Click to expand...
I've always <"been a rainwater user">, and it would always be my preferred option.

cheers Darrel
 
I'd be inclined to assume they are appearing in the transition phase, and much like with a new tank setup will probably resolve themselves so wouldn't worry overly about trying to fix them as you might be chasing a problem that isn't one.
 
Hi all,
Sanniejop said:
You mean something like this?
Click to expand...
That is it. You often get a <"flush of algae"> appearing if a, formerly, non-available, nutrient becomes plant available.

Because algae take nutrients directly through the cell membrane they can respond very quickly to changes in nutrient availability. Diatoms are the slightly strange item, and not something you would expect to suddenly appear in an established tank.

Iron (Fe) is the <"most normal deficiency"> we see in harder, more alkaline water, but <"manganese (Mn) is a possibility"> and you can get a high Ca++ : Mg++ ratio interfering with magnesium uptake etc.

If you look at @Roland 's <"Soft water tank"> you can see that the <"water parameters he has created"> allow him to grow a lot of "difficult" plants extremely successfully.

cheers Darrel
 
Last edited:
Just a random thought; @Sanniejop you say collect the water from a roof with gravel. I think perhaps an easy way to determine if anything leaching off the roof would be to compare the TDS/EC of a sample taken from the water coming off the roof and a sample just collected in a clean glass. If you are collecting the water in an area with air pollution (acid rain) I guess it potentially could make the roof / gravel leach out something. Perhaps a bit far-fetched, what say you Darrel (@dw1305) ?

Cheers,
Michael
 
MichaelJ said:
Just a random thought; @Sanniejop you say collect the water from a roof with gravel. I think perhaps an easy way to determine if anything leaching off the roof would be to compare the TDS/EC of a sample taken from the water coming off the roof and a sample just collected in a clean glass. If you are collecting the water in an area with air pollution (acid rain) I guess it potentially could make the roof / gravel leach out something. Perhaps a bit far-fetched, what say you Darrel (@dw1305) ?

Cheers,
Michael
Click to expand...
The TDS is around 3ppm. I dont know if this low enough for clean rain water.
 
Hi all,
MichaelJ said:
Just a random thought; @Sanniejop you say collect the water from a roof with gravel. I think perhaps an easy way to determine if anything leaching off the roof would be to compare the TDS/EC of a sample taken from the water coming off the roof and a sample just collected in a clean glass. I guess it potentially could make the roof / gravel leach out something. Perhaps a bit far-fetched, what say you Darrel (@dw1305) ?
Click to expand...
I think it is a good idea, I'd be surprised if there was much difference, but it would show for sure.
Sanniejop said:
What is in your opinion the right ratio for those elements?
Click to expand...
Just "some magnesium (Mg)". I think the recommended ratio is 3 : 1 Ca : Mg.
Sanniejop said:
The TDS is around 3ppm. I dont know if this low enough for clean rain water.
Click to expand...
That is incredibly pure, you wouldn't necessarily get a value that low from a distillation unit.

Cheers Darrel
 
Bought the tds meter one month ago. I read that it was already calibrated. Directly ready for use.
I hope it is working well. Temperature is 14 degree celcius.
 

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Sanniejop said:
Bought the tds meter one month ago. I read that it was already calibrated. Directly ready for use.
I hope it is working well. Temperature is 14 degree celcius.
Click to expand...
Did the pen not come with calibration liquid? Mine came with calibration liquid of 342ppm to ensure that is reads correctly
 
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