Water Chemistry Newb Question

[airdrieaquarist]

Hi all. I live in airdrie and I recently introduced a wack load of plants into my 200 gallon tank.

I have a pressurized co2 system with a ph controller. My problem is with PH/KH.

As you know, the tap water comes out at PH 7.9 - 8

I'm introducing co2 at a fairly high rate (around 3-5 bbls /sec) but I don't seem to be able to get my Ph to go below 7.75

I'm aware of the dangers of changing the ph/kh too fast , but that does not seem to be a problem because I can't get the ph to drop.I'm going to dial down the co2 to 1 or 2 bbls. From the chart I looked at, ph 75 and kh 7dkh means my dissoved co2 is only at around 7 mg/ L which is at least half of what it should be. Am i out to lunch?

my co2 drop checker seems to be sitting green which (from what I understand) means that my dissolved co2 levels are at or above acceptable.

My KH reading is 7 dkh and my GH is 14dkh. now correct me if I'm wrong but the 7dkh is the main reason why my ph won't drop anymore.

These numbers are just too high for plants. my anubias seems to be fine, but i would like to start introducing a bunch of other plants.

How do others in the area deal with these high kh/ph values? also - what does the crazy high gh of 14dkh mean in my situation?

Thanks in advance.

[SuperGuppyGirl]

I am not familiar with C02 systems, but am wondering what lights you have going? For harder water, some I have heard recommendend with African cichlids should work,

Anubias

Java Fern

Java Moss

Jungle Vials

Water Sprite

Amazon Swords

Onion plants

All low tech, low maintenance plants

[Znaika]

pH can drop rapidly only in water with low carbonate hardness, which Alberta water is not.

When you add carbon dioxide to water it forms carbonic acid: CO₂ + H₂O -> H₂CO₃. The reaction goes in the opposite direction too: H₂CO₃ -> CO₂ + H₂O. Which reaction is "stronger" depends on CO₂ concentration in water, so with lots of CO₂ you achieve higher concentration of H2CO3 in water.

But this is only a half of the story.

Then this acid breaks apart in water: H₂CO₃ -> H⁺+ HCO3^-. Higher concentration of H⁺ ions defines low pH. However water with high KH contains lots dissolved carbonates (and bicarbonates), for example: M²CO³ -> M²⁺ + CO3^-. The latter negative ions (in bold) "capture" H⁺ ions, keeping their numbers low and thus not allowing pH to drop. Until such negative ions of carbonates and bicarbonates are present in sufficient concentration, they will not allow pH to go down, or, as they say, they will "buffer" water.

You need to reduce KH down to 2 or lower to see noticable fluctuations of pH as a result of adding CO₂ into water. You can do it by adding acid salts like Seachem's acid buffer or 10% sulfuric acid or by filtering water through a bucket of peat moss, which is safer, but arguably messier and less efficient.

Edited February 26, 2013 by Znaika

[Jro]

What plants are you putting in? I am no expert but I found a lot of plants to be tolerant of pH differences as long as it remains consistent.

[airdrieaquarist]

pH can drop rapidly only in water with low carbonate hardness, which Alberta water is not.

When you add carbon dioxide to water it forms carbonic acid: CO₂ + H₂O -> H₂CO₃. The reaction goes in the opposite direction too: H₂CO₃ -> CO₂ + H₂O. Which reaction is "stronger" depends on CO₂ concentration in water, so with lots of CO₂ you achieve higher concentration of H2CO3 in water.

But this is only a half of the story.

Then this acid breaks apart in water: H₂CO₃ -> H⁺+ HCO3^-. Higher concentration of H⁺ ions defines low pH. However water with high KH contains lots dissolved carbonates (and bicarbonates), for example: M²CO³ -> M²⁺ + CO3^-. The latter negative ions (in bold) "capture" H⁺ ions, keeping their numbers low and thus not allowing pH to drop. Until such negative ions of carbonates and bicarbonates are present in sufficient concentration, they will not allow pH to go down, or, as they say, they will "buffer" water.

You need to reduce KH down to 2 or lower to see noticable fluctuations of pH as a result of adding CO₂ into water. You can do it by adding acid salts like Seachem's acid buffer or 10% sulfuric acid or by filtering water through a bucket of peat moss, which is safer, but arguably messier and less efficient.

Excellent info but I will admit - a bit beyond me. I think what you are saying here is that because I will be doing weekly water changes (or bi-weekly), I will never get rid of my high PH unless i unless (in addition to a de-chlor) I use KH reducing additives (Sulfuric acid/acid buffer/peat) everytime I change water. It also sounds like my best option here (I eventually plan on moving my cichlids to a different tank so I can go full - plant) is to invest in a RO/DI system and use that water for my partial changes. If this is the route I choose, could I get away with just using a 2-stage RO system as opposed to a 4 or 5 stage RO/DI? Thanks for all the info btw

[airdrieaquarist]

What plants are you putting in? I am no expert but I found a lot of plants to be tolerant of pH differences as long as it remains consistent.

Because my tank is currently inhabited by African Cichlids, I only have some really large Anubias on driftwood (About 6 big plants all 12 inches x 6 inches with a total of about 40 large leaves.). They are doing ok now but i know the PH is starting to affect them.

My lighting is a bit overkill. White Metal H 3x 150 watt and 4 x blue T5HO.

I have started to reduce the duration of lighting to about 8 hours /day and I'm leaving only 2 of the MH lighjts on instead of 3. I will likely reduce it to one light shortly but once I get the PH/KH stable to where I want it, I will get all the plants I want and increase the lighting.

[Znaika]

Excellent info but I will admit - a bit beyond me. I think what you are saying here is that because I will be doing weekly water changes (or bi-weekly), I will never get rid of my high PH unless i unless (in addition to a de-chlor) I use KH reducing additives (Sulfuric acid/acid buffer/peat) everytime I change water. It also sounds like my best option here (I eventually plan on moving my cichlids to a different tank so I can go full - plant) is to invest in a RO/DI system and use that water for my partial changes. If this is the route I choose, could I get away with just using a 2-stage RO system as opposed to a 4 or 5 stage RO/DI? Thanks for all the info btw

You've got it right. Your options are:

1) invest into RO system - high upstart cost and expensive to maintain, low output, but readily available and provides not just low KH, but also low dH water. However you do not want to lower dH until you relocate your African Cichlids.

2) buy RO water (~$3 per 5 gallon) - same advantages as above, plus low upstart costs, but expensive on the long run plus involves a lot of physical exercises.

3) "cook" water by adding acid or acid buffer - inexpensive but involves large pails with water, hassles and time (a day or two of constant aeration for the chemical reactions to complete).

4) filter water through peat moss - also inexpensive and "organic", but messy, not very efficient and colours the water.

For 200 gal tank 2) and 4) are not practical. Your choice is between 1) and 3). If you need low dH, then the choice is down to 1) only. If 7°dH water is acceptable, then I would go with 3) as this option is cheaper and simpler: it is easier to quickly fill up 50 gal rain barrel and to cook it for a day than to trickle up 50 gal of RO water using RO system and changing membranes every few months.

Edited February 26, 2013 by Znaika

[creekbottom]

I've never had a problem growing anything I wanted in Edmonton tap water. You could also look into a substrate that will buffer your water so the pH comes down.

I've experimented with Optisorb and capped it with sand. It brings the pH down to the low 7's, right in between the high and low pH tests in the API kit lol. It has a high CEC and its crazy cheap!

[cullymoto]

I'm sorry I cant help you with Co2, I have no experience with it.

And I'm a bit off topic here...if your looking for a plant grow tank r/o may not be the best option...

I have a 3 stage r/o (whirlpool), it is a 30 gpd unit with a small booster pump inline to make it run 45 - 50gpd. way more than it was designed to run. I have been running it nearly constantly ( ie; it is always working to refill my storage tank + we drink it, as soon as the storage tank is full I do a large water change on my 125gal discus tank) for a year. the cartridges are designed to run 30 gpd for 6 months then be replaced. I run it at 45 - 50 gpd for 14 months now and still reads 0 ppm gh, 0 kh, 0 chlorine/chlorimine, and ph 6.0.

so long as it maintains these kind of figures i do not plan on replacing the cartridges... if they require a change it will cost $100.00

Initial start-up cost was sub $400 + my time to install it (3 on a 1-10 difficulty scale) and a higher water bill since installing it.

These test results are not right for african cichlids...or plants. They both need minerals in the water column. You would be adding kh, gh, and ph to your water to make it suitable for them.

for south american cichlids this water is much closer to ideal, I just have to add kh.

Hope this is of help.