Trying to understand Kh and GH

[Biollante]

Hi,

A correction, my apologies, sometimes I spend so much time looking at the trees and I miss the forest.

A TDS of 1270-ppm is 1.27 parts per thousand and anything over 1-ppt is too high for most freshwater plants and critters, aside from some Lake Tanganyika or Lake Malawi critters. Generally as TDS reaches 500-ppm or 0.5-ppt some of the "rules" change.

I think the RO water is a good idea and I would recommend at least 2-parts RO to 1-part tap, 3 or 4-parts RO to 1-part tap water is even better.

Biollante

[sandeepraghuvanshi]

It has been a week since I got ph & tds meters.
I have been testing on a daily basis, the average of reading is as below

Parameter | Source - | RO | Aquarium
PH | (7.6 to 8.2) - | ( 6.8 to 7.1) | ( 6.2 to 6.5)
TDS | (1150 to 1220) | (48 to 51) | (870-890)

All readings at taken in evening.

Now I am changing 80 lits of water every week, out of this 50 lit is RO water about 63%.
I think I will wait for my GH, KH test kits, and then decide if to change the ratio of RO water

[Biollante]

Hi,

You are going to need to do substantial water changes to get TDS under 500-ppm. I suspect you will be much happier once you get into the 200-250-ppm TDS.

With or without test kits of any sort you will need to increase the percentage of RO water, the tap water information alone is enough to go on. Unless you want a brackish aquarium or Lake Malawi African Cichlid tank, I am partial to Lake Malawi Cichlids myself. I do not have much experience with Lake Tanganyika critters but they are spectacular as well.

I will treat the ranges you provided as averages by adding the two numbers you provided by two. To provide an average I need all of the numbers.

The 80-liters you are using to change the water still has a TDS around 475-ppm.

Since I do not know the size of your aquarium all I know is the net reduction of 710-ppm for the 80-liters replaced. If it is a 100-liter aquarium, you will be in passable shape in a couple of weeks.

An RO system ought to be able to knock the TDS down to single digit parts per million. Your RO may require a new membrane; a good charcoal block filter in front will help preserve the membrane as will a pump to ensure proper pressure across the membrane.

Biollante

[sandeepraghuvanshi]

Hi,

You are going to need to do substantial water changes to get TDS under 500-ppm. I suspect you will be much happier once you get into the 200-250-ppm TDS.

With or without test kits of any sort you will need to increase the percentage of RO water, the tap water information alone is enough to go on. Unless you want a brackish aquarium or Lake Malawi African Cichlid tank, I am partial to Lake Malawi Cichlids myself. I do not have much experience with Lake Tanganyika critters but they are spectacular as well.

I will treat the ranges you provided as averages by adding the two numbers you provided by two. To provide an average I need all of the numbers.

The 80-liters you are using to change the water still has a TDS around 475-ppm.

Since I do not know the size of your aquarium all I know is the net reduction of 710-ppm for the 80-liters replaced. If it is a 100-liter aquarium, you will be in passable shape in a couple of weeks.

An RO system ought to be able to knock the TDS down to single digit parts per million. Your RO may require a new membrane; a good charcoal block filter in front will help preserve the membrane as will a pump to ensure proper pressure across the membrane.

Biollante

Tank size is 36X18X18, leave aside substrate 2", water voume is 170 lit.
Wc every week 80lit = 50 lit RO+30 lit Tap water.

Source water Gh 520 ppm, Ro 50 ppm(need to confirm this once test kits arrive)
I started on 1-6-2012,
gh on 7-6-2012-= 382
I have calculated it by (90*520+50*50+30*520)/170

So after one month gh should be 238ppm or 13.32
Do you concer with my calculations.?

[Biollante]

Hi,

I may be confused, happens pretty regularly, but…

While I agree (90*520+50*50+30*520)/170 = 382, I do not understand the relevance or where the 238ppm GH comes from.

I was under the impression the “50” (ppm is my assumption) was TDS. I have no way of knowing the percentage of Calcium and Magnesium in the 50 (presumed ppm) TDS reading.

I think you are inferring (from post #8) that since total hardness was 520-ppm GH and TDS was 1270-ppm that since (520 ÷ 1270) X 100 = 41% so 41% of 50-ppm RO water (20.5-ppm) must be GH.

Even assuming that you get the general hardness down to 238-ppm GH, 46% of its original level that means alkalinity is still 149-ppm KH. Total dissolved solids, TDS is still going to be 584-ppm (0.584-ppt).

The problem is the total amount of stuff in the water.

My sense is that you have made up your mind a certain mix of RO. You are of course free to do as you please.

Anyway, my advice is 3 or 4 parts RO to tap water without regard to test kits or results that is just the arithmetic. In fact, save your money on test kits and invest in filtration.

Best of luck,
Biollante

[Biollante]

Hi,

The cation and anion do not really add up.

I suspect there is something like 335-ppm of Sodium in there as well, even with that added the analysis is off.

I also calculate the osmotic pressure 82.08-kPa, so that would require an operating pressure for an RO membrane of 228-kPa, the reason your RO is only getting down to 50-ppm TDS is that it is a freshwater membrane and it appears you require a brackish or seawater membrane.

Or some good filtration in front of the RO filter.

Biollante

[sandeepraghuvanshi]

Hi,
I may be confused, happens pretty regularly, but…
While I agree (90*520+50*50+30*520)/170 = 382, I do not understand the relevance or where the 238ppm GH comes from.
I was under the impression the “50” (ppm is my assumption) was TDS. I have no way of knowing the percentage of Calcium and Magnesium in the 50 (presumed ppm) TDS reading.
I think you are inferring (from post #8) that since total hardness was 520-ppm GH and TDS was 1270-ppm that since (520 ÷ 1270) X 100 = 41% so 41% of 50-ppm RO water (20.5-ppm) must be GH.
Even assuming that you get the general hardness down to 238-ppm GH, 46% of its original level that means alkalinity is still 149-ppm KH. Total dissolved solids, TDS is still going to be 584-ppm (0.584-ppt).
The problem is the total amount of stuff in the water.
My sense is that you have made up your mind a certain mix of RO. You are of course free to do as you please.
Anyway, my advice is 3 or 4 parts RO to tap water without regard to test kits or results that is just the arithmetic. In fact, save your money on test kits and invest in filtration.
Best of luck,
Biollante

First of all tanks a lot for applying that much time to my posts.
Now as I do not have a gh test kit, I do not know the gh or kh of my Ro water, so just for calculation purpose I have used 50 as gh also, ( a fool's assumption, I know)
Now TDS of my aquarium water is 800-900, seems to vary a lot, is temp a issue here.
Now you have advices 60-75% of RO water, now is this % of water change I am making or to the total water in aquarium.
Currently I am mixing 50 lit of Ro water with 30 lit of tap water, which gives me a ratio of 63%

[sandeepraghuvanshi]

This is the filter I am using, it is for kitchen purposes
http://www.eurekaforbes.com/water-pu...al-reviva.aspx

[sandeepraghuvanshi]

BTW, this is the tank which us under discussion.

http://www.barrreport.com/showthread...Light-Co2-tank

[Biollante]

Hi,

You are welcome!

I do not mean to be aggravating, I just am. Some situations catch my attention and I like to understand.

• It really is just arithmetic.

I think you need to do a series of large water changes to get to a point where 75-80% of the water is RO.

• The reason for a series of water changes is to avoid shock to the critters and biological filtration.

The fact is that as your tank is now brackish.

Mollies are a good choice as they are critters that do well in brackish water, it may not be necessary to bring the water all the way down, if you choose plants and critters that tolerate higher osmotic pressures.

It is important to get under 500-ppm (0.5-ppt), from what I see in your tank and based on your description getting under TDS 400-ppm would be great.

• 450-ppm TDS is a little over 2-parts RO to 1 part tap (66.66%).

Your RO device is a bit underpowered, I calculate you would need 228-kPa the unit you have is capable of 196-kPa so 50-ppm TDS is probably doing quite well. The higher the input water temperature generally the less efficient the filter, yours claims input water temperature up to 45°C, my guess is the efficiency is somewhat lower at the high end.

Are you using the "high TDS" membrane?

Is the water chlorinated?

Is the tap water microbiologically safe? I bring this up only because I see they advertise

• “It also helps protect your family from water-borne disease-causing bacteria, viruses and protozoa. It also eliminates harmful disease-causing chemicals like pesticides and more, ensuring that every drop of water your family drinks is pure and safe.”

If 50-ppm TDS can get through, then so can other stuff. I caught the Silver Impregnated, to kill protozoans, I cannot find any information, explaining how it works (how much silver enters the water column) this could be suppressing your biological filter that would help explain the scum.

My assumption is that they are using standard 2.5 inch TFC Spiral RO Membrane, so you should be able to replace it with a brackish water membrane, which will lower the pressure required and you should be able to get down into the single digit TDS.

Biollante