Whats In Our Tap Water?

[Miss Wiggle]

some of you may know Ian's had problems with his planted tank, it very rarely pearls at the moment, we've noticed it only does after water changes. then i noticed last week after doing a water change on my big tank that the swords were pearling too!! It's a juwel trigon 350 with bog standard lighting, tubes well over a year old, no Co2, no ferts (well it's got an oscar and a plec in but aside from poop there's no ferts added!) it's not geared up for plant really but it's got a few big amazon swords in there. They grow slowly but are growing so they're just doing OK basically.

So anyway I figure thee must be something in our tap water that makes the plants pearl after water changes, wanted to suss out what it is firstly out of curiosity and cause it could help sort out Ian's planted tank. So can you give me an idea of what elements could be in there to be making things pearl and I'll try and test it for them.

 

[Dave Spencer]

In a Juwel tank with standard lights, no CO2 and no ferts I wouldn`t have thought the plants would have been metabolising quickly enough to produce O2 bubbles.

Maybe you get pearling straight after a water change because your tap water contains a reasonable amount of CO2. Plus your plants may have been taking in Carbon from the atmosphere when they are exposed during the water change.

I think I read a thread about this somewhere else a while ago.

Dave.

 

[Miss Wiggle]

you have to forgive my ignorance a bit, i do try and understand the science behind planted tanks but i've not got my head around it all yet.

there's a method for testing Co2 where you measure the pH drop after leaving it to stand for 24hrs or something like that isnt there? how do you do it exactly and would it work testing the tap water?

 

[dave_gray2077]

Its usually not pearling you are seeing if its just after a water change. It’s mainly due to small pockets of air that are trapped and introduced in the pipes on its way to your house. Once the water settles in your tank they congregate together.

If it is actual pearling you are seeing it’s mainly due to the CO2 content of tap water. Fresh tap water will have a higher ppm count.

As you are not adding any fertiliser the pearling will also be caused by just about everything in you water. After the water change you are providing the plants with what is essentially a dilute trace element mix.

This behaviour may (probably the most likely) indicate large Potassium ppm count in your water. Do you have a water softening ball device on your drinking water pipe? As they contain large amount of potassium based salts like potassium chloride etc.

May be worth checking the Potassium contact of your water from the tap and then the tank and compare the results.

 

[Miss Wiggle]

It is definatlety pearling, i know you can get air bubbles after the water change and it's after that's all settled down like 4/5 hrs later we'll notice pearling.

i've no idea what a water softening ball device is let alone if we have one but i'll ask Ian! I'll try and check the potasium content too, is there a test kit you can get for it or some funny way of testing like with Co2?

 

[Dave Spencer]

Leave a sample of your tap water open to atmosphere for 24 hours, then measure the pH. At the same time, measure the pH of a sample straight out of your tap. You should notice a higher pH in the water straight out of the tap because the 24 hour sample will have degassed its CO2 to equilibrium with the atmosphere ie the higher CO2 concentration in the tap water equalises with the lower CO2 concentration in air.

Make sure you also measure the KH of your tap water, then you can estimate the CO2 levels using the KH/pH chart.

Adding extra light or CO2 are two sure fire ways of kicking your plants in to life and causing pearling. You haven`t adjusted your lighting, so it is likely to be the CO2 content of your tap water.

Hope this helps, Dave.

 

[Miss Wiggle]

thanks I'll try testing our tap water for Co2. is there any guidelines to how much Co2 should be in your tap water? any healthy/unhealthy levels in terms of it being drinking water or does it not affect anything like that?

 

[nry]

There'll be more CO2 in your average fizzy drink I would have thought. The test on high levels in water is to see if you start producing oxygen bubbles when swimming under full sun.

 

[George Farmer]

Plants can also "leak" O2 from damaged leaves, which is different to pearling.

 

[Miss Wiggle]

There'll be more CO2 in your average fizzy drink I would have thought. The test on high levels in water is to see if you start producing oxygen bubbles when swimming under full sun.

ah yes, good point!

Plants can also "leak" O2 from damaged leaves, which is different to pearling.

yeah it's definatley not that either, we had a really good look as we were so surprised to see pearling in that tank!! the leaf it was coming from was the biggest tallest one, it's undamaged and just had a little stream of tiny bubbles coming out of near the end of the leaf. we checked the point it was coming from, couldn't find any breaks/cracks or anything like that.

 

[JamesC]

Do the water change a few hours before lights on and watch. If you get bubbles then you know it's water degassing. If not then the increased pearling is due to photosynthesis. Doing large water changes often allows the plants catch CO2 directly from the atmosphere when they are exposed increasing O2 production - this is a trick that can be used to create greater pearling for photo's.

Increased pearling after water changes can also be due to low ferts in the tank. Tap water can contain NPK, CO2, so after a water change plants take off until levels are depleted again.

James

 

[Miss Wiggle]

interesting, i'll try doing oscars next water change before the tank lights come on.

 

[mlawson]

Tapwater contains almost nil CO2.

 

[JamesC]

Tapwater contains almost nil CO2.

What makes you say that? Depending on where your water comes from it can have quite a lot of CO2 dissolved in it.

James

 

[JamesC]

Here's what Tom Barr has said on this issue of CO2 in tap water.

It's entertaining to suggest a myth vs fact on such topics.
As someone who has a water treatment operators license, I can tell you that most tap has more than ambient, and a lot of tap water is really loaded, well/spring water in particular.

I'll present my case easily here:
Caves, you know, the places folks crawl around in, my Dad was a cave biologist.
How are they formed? CO2..........
Why would ground water be loaded with CO2?

As rain falls, it enters the soil, bacteria give off XCO2, that's absorbed by the water, but there is nowhere for it to off gas. So it builds up and becomes rich in CO2, this eats away at limestone, which is a nice base that reacts well with CO2=> caves are formed.
Typical CO2 ppm in spring water: 10-30ppm in Florida, KY, IN, OH, AL, NC, SC, IL, MS, AR, TX, NM, CA, MN, WI, MI, NY, PN, WV, VA, TN..... anywhere there's limestone and many places there isn't. Not all tap will be loaded, but __most__ is. Ground water is almost always much higher.

Why would cold tap have more CO2 than your warm tank water?
Water at a colder temp holds more gas than at ambient conditions.
All gases...............

Those are the "facts" about tap water.