CO2 level and excel

[phin]

Based on another thread:

CO2 ppm = 12.838*dKH*10^(6.37-pH)

My planted tank is 18 gallons (10x20x20), lighting is 15w T8 5000K, 13w CFL 6500k, 10w CFL 6500k.

last week I changed my substrate from 3-year-old, mulm-caked gravel to flourite over peat moss.

I have been dosing:
Seachem floruish excel (1.875ml 1x/day)
Seachem flourish (2ml 3-4x/week)
API leaf zone (10ml 2x/month)

prior to my substrate change my water parameters were:

dKH - 11
dGH - 16
pH - 7.8
Nitrate <15ppm
Nitrite 0ppm
Ammonia 0ppm
Phosphate 1.3ppm

Based on the formula above my CO2 concentration was 5.25ppm CO2. I had a pretty bad BBA problem.

Since I've made the substrate change I have been dosing with Seachem acid buffer in order to remove KH. I'm also on my second go-around of an API water softener pillow to decrease my GH. I added peat to my substrate as well as run peat in my canister. I've increased the bioload in my tank by adding a botia striata (zebra loach) and 3 tiger barbs. All of this with the intention of softening the water and lowering the pH.

My current water parameters are:

dKH - 4
dGH - 8
pH - 6.9
Nitrate <10ppm
Nitrite 0ppm
Ammonia 0ppm
Phosphates <0.25ppm

Based on the formula, my CO2 concentration has increased to 15.15ppm CO2.

Does anyone know the effect dosing excel has on CO2? I understood it to not effect CO2 concentrations, but add an available carbon source to be used in photosynthesis instead of CO2.

If I keep my phosphates down, how much of an effect on the BBA will I have? (there is very little BBA left after my plant & driftwood cleaning/substrate change out).

It also seems to me that absent CO2 infusion, lowering my pH from 6.9 to 6.5 while keeping my dKH at 4 will increase CO2 to 38ppm.

Are these maximum concentrations, or is this formula actual concentrations?

 

[ztigris]

While I can't answer your Co 2 questions. The algae is effected by your photoperiod as well. How long do you leave your lights on?

 

[phin]

I had them on 11 hrs/day. I have cut that back to 8hrs.

 

[Rivercats]

I can't help with the CO2 either as I only use liquid carbon but there are two things here that need to be addressed. First the water softner pillow is not a good idea to use. All your doing is exchanging Calcium and Magnesium ions with Sodium Ions. Sodium in a planted tank is not a good thing. At least the plants can use some calcium and magnesium. If you want to soften your water its better to use a mix of RO water with your tap water to achieve the GH/KH you want. That also means you don't need to use a Ph acid buffer which is also not a good thing to do.

Plants also need phosphates as it is a macro nutrient. Your level is very low and I have not found BBA to be an issue with higher phosphate levels. I actually run my tank low nitrates and high phosphates of around 1.5ppm.

 

[phin]

I can't help with the CO2 either as I only use liquid carbon but there are two things here that need to be addressed. First the water softner pillow is not a good idea to use. All your doing is exchanging Calcium and Magnesium ions with Sodium Ions. Sodium in a planted tank is not a good thing. At least the plants can use some calcium and magnesium. If you want to soften your water its better to use a mix of RO water with your tap water to achieve the GH/KH you want. That also means you don't need to use a Ph acid buffer which is also not a good thing to do.

Plants also need phosphates as it is a macro nutrient. Your level is very low and I have not found BBA to be an issue with higher phosphate levels. I actually run my tank low nitrates and high phosphates of around 1.5ppm.

So the water softening pillow is an ion exchange resin? I guess that makes sense. I should have looked into it a little more before hand. How much sodium is harmful? I would think there would be a trade off between the hardness of the water and the sodium level. Also I don't want to remove all the calcium or magnesium from my tank, just reduce the GH from 16 to ~5, which will still leave calcium and magnesium available for the plants. Dragging 15 gallons of RO from my LFS is inconvenient for me, I plan on keeping a couple gallons of DI on hand to top off any evaporation.

Why do you caution against the acid buffer? For me its worked great. For years I was cautions about doing anything to change my pH or KH, but now I've decided to give it a shot. I measure out the acid buffer to the 0.1 gram and put in exact amounts, directly on the floss of my HOB, it dissolves within 30 seconds. I measure my KH and pH beforehand and 1 hr afterhand. Everything has been predictable and stable. It isn't something I intend to use on an onging basis. In fact, I plan on adding 1.5g tonight and being done with it. That should reduce my KH from 4 to 3 dKH. Since I have never needed to do regular water changes on this tank I won't need to mess with the chemistry of the water (hopefully, but I'll be monitoring it).

Thats great news on the phosphates. I was afraid that was the cause of my BBA, but I'm beginning to think it was due to low CO2 concentration. That should be resolved by lowering my pH. If I can get a stable pH of 6.4-6.6 my CO2 concentration should be at a higher level than BBA enjoys.

But then again I may be wrong.

 

[Rivercats]

The problem with buffers in general but in your case acid buffers is they are only a temp fix. You add them, the ph drops, then within a day or so the ph rebounds back up and you have to add acid buffer again. All those chemicals are not good for fish and they are only a temporary fix. Once you stop using them your ph will rebound back up. Also why don't you do regular WC's?

 

[phin]

The problem with buffers in general but in your case acid buffers is they are only a temp fix. You add them, the ph drops, then within a day or so the ph rebounds back up and you have to add acid buffer again. All those chemicals are not good for fish and they are only a temporary fix. Once you stop using them your ph will rebound back up. Also why don't you do regular WC's?

I'm not using the Acid buffer to lower the pH directly. I'm using the acid buffer to reduce my KH, or remove my alkaline buffering capacity. i will stop using the acid buffer when my KH reaches the desired level. Unless I add an alkaline buffer then the KH should remain stable.

Once I have a low buffering capacity, I intend to lower my pH naturally by filtering with peat (pH 4.5), in addition to the bioload of the tank which will create a small amount of nitric acid, and plant resperation which will create carbonic acid during non-photoperiods.

I don't do regular water changes because I've never had a nitrate problem in that tank. Once my plants became established Ammonia & Nitrite was always 0 and Nitrates were less than 15ppm every time I tested the water. Over the past two years I've probably done less than 10 water changes of 5 gallons or less.

It was the result of minimal water changes, I believe, that was the cause of my phosphates to rise to 1.5ppm. If your hypothesis is correct, I shall not worry about that level of phosphates in my tank.

 

[Rivercats]

Water changes are needed to remove pollutants that plants and fish produce – you can’t see them, but they are there in the form of dissolved organic. When plants grow, they produce waste. Fish waste and food adds more dissolved organics. These waste products (organics) need to be removed, otherwise they build up, become more concentrated and then cause you problems such as algae. Water changes not only remove dissolved organics they also add minerals and nutrients to the water.

 

[phin]

Water changes are needed to remove pollutants that plants and fish produce – you can’t see them, but they are there in the form of dissolved organic. When plants grow, they like everything else that grows they produce waste. Fish waste and food adds more dissolved organics. These waste products (organics) need to be removed, otherwise they build up, become more concentrated and then cause you problems such as algae. Water changes not only remove dissolved organics they also add minerals and nutrients to the water.

That makes sense. I guess its not all about nitrates. If I'm not worrying about nitrates do you think I could get away with 5-10% week (1 gallon) to control dissolved organic waste?

I'd rather pick up a gallon of distilled or DI water from the grocery store each week than worrying about hauling RO from my LFS. When water is advertised on the shelf as DI do you know if it is typically RO/DI or just DI?

I don't want to have to keep adding the acid buffer and I want to keep my GH down, so I don't want to use my tap water after I've achieved my target levels. Most likely I will use distilled or DI water from the grocery and add seachem equilibrium to it until I match the tank's parameters.

 

[Rivercats]

I actually do 50% WC's weekly even on my 220g but if all you can do is 10% it's going to be better than nothing. If you could up it to at least 20%, 2 gallons of RO, I think it would be better at removing organics from your water. I'm not sure about those grocery store units but I always thought I read on the front of them RO water, at least the ones in my area. I have an RO unit so I haven't bought RO water like that for years.

 

[phin]

An RO unit would be sweet, but thats not an option. My LFS sells RO for $0.50/gal but I don't believe it is DI as well, I've bought it before and it wasn't worth the trouble. I think what I'm going to do is buy a gallon of each of the different types of water they have at the store, test each one and see if any give me the GH KH & pH levels I desire. If not I'll go with RO/DI from the store and add equilibrium to it.

 

[ztigris]

Most water vendors (culligan, store vending machines) provide RO for 25-30 cents a gallon. RO removes the hardness distilled doesn't. Walmart has a 5 gallon container for $8 and culligan sometimes has used 5 gallon containers for $7. It costs me $3.00 for 10 gallons of ro every week. Totally worth it since my tap is liquid rock.

 

[aqua_chem]

Excel and CO2 are completely unrelated from a chemistry perspective here. The levels of Excel wont affect CO2, and vice versa.


That aside, the CO2-KH-pH equation makes a few critical assumptions, most importantly that carbonate is the only buffer in the system. Without that being true, the equation is meaningless. You have unfortunately violated that conditions pretty handily with the addition of peat and commercial pH changers, so your calculations are ultimately meaningless.

That being said, if you are not injecting CO2, your CO2 concentration is about 3.

 

[phin]

Excel and CO2 are completely unrelated from a chemistry perspective here. The levels of Excel wont affect CO2, and vice versa.


That aside, the CO2-KH-pH equation makes a few critical assumptions, most importantly that carbonate is the only buffer in the system. Without that being true, the equation is meaningless. You have unfortunately violated that conditions pretty handily with the addition of peat and commercial pH changers, so your calculations are ultimately meaningless.

That being said, if you are not injecting CO2, your CO2 concentration is about 3.

Thanks. Thats the main point I was trying to get to and some good points on the equation. I'l keep dosing with excel, but I will think about CO2 injection, however, right now I'm not even putting it in the conceptual stage. If I do inject CO2 in the future, while filtering with peat, would there be a way to measure CO2 in ppm?

The acid buffer says it contains bisulfate salts. which I believe is actually sodium bisulfate NaHSO4 however, since the acid buffer is so powerful, such a relatively small amount is used, and it isn't used every day once my KH is set, the sodium that remains after the chemical reaction is negligible.

Now that I type this out, it does seem like the hard way to do it. Just sticking with RO/DI or distilled water and reconstituting. I figured, reconstituting or deconstructing the water is like "six in one or a half-dozen in the other. "

As a side note, I got my dKH down to 3 last night with a final dose of 2.5g of sodium bisulfate. The drop in dKH from 4 to 3 had the most significant impact on my pH. My pH went from 6.9 to 6.4. I will take measurements again tonight and see where the pH rebounds to. I'm expecting with a KH of 3 that my pH won't rebound to 7.0 and will stay 6.4-6.7, if so, then I'll maintain that level and do weekly 1 or 2 gallon water changes with RO/DI or distilled water and reconstitute with seachem equilibrium to match my GH and some baking soda to achieve a KH of 3. It will take a little experimenting to get the measurements right before hand, but I expect it to work out.

]Most water vendors (culligan, store vending machines) provide RO for 25-30 cents a gallon. RO removes the hardness distilled doesn't. Walmart has a 5 gallon container for $8 and culligan sometimes has used 5 gallon containers for $7. It costs me $3.00 for 10 gallons of ro every week. Totally worth it since my tap is liquid rock.

I think you are mixing up distilled water with DI (de-ionized) water. Distilled water removes almost all of the GH through the steam-distillation process, which is why distilled water is used in chemistry labs, and industrial applications where steam is used so mineral deposits don't add up. De-ionized water uses chemical filtration to remove the mineral ions (cations like sodium, calcium, copper & anions like sulfate and chloride). Distilled water is also not 100% H2O, hence the necessity for twice-distilled and triple-distilled water to increase purity for certain applications.

Combining reverse osmosis and de-ionization (RO/DI) water makes extremely pure water, however I don't believe my LFS goes through the DI process and only produces RO water, not RO/DI water, which makes it a hassle for water that I still need to deconstitute before I add to my tank. Which is why I'm considering using distilled water from the grocery store, or the DI water they advertise, hoping it is RO/DI; I will test the waters they sell to find the right one.

 

[ztigris]

Actually (at least in my local) most of the vendors run 3 types. RO, DI, and carbon. Where most bottled spring water is only distilled or a combo of distilled and RO. Which is why I use the vendored water. It is the only way I can cut my gh/kh down.

 

[aqua_chem]

Now that I type this out, it does seem like the hard way to do it. Just sticking with RO/DI or distilled water and reconstituting. I figured, reconstituting or deconstructing the water is like "six in one or a half-dozen in the other. "
one.

It's actually quite different. When reconstructing, you can only add; when "deconstructing", you can only exchange, not subtract. Subtraction requires energy investment, which is why we need to go to such great lengths to make RODI water. When you soften water, you're usually exchanging calcium and magnesium for either sodium/potassium (water softening pillows, home water softeners) or protons that lower pH (some ion exchange resins, peat). You can see where this would be very limiting if you want to finely control your water conditions. That being said, there are relatively few circumstances where you need this kind of control.


Also, distiller water should have the vast majority of salts removed, including the carbonates that contribute to KH.

 

[phin]

It's actually quite different. When reconstructing, you can only add; when "deconstructing", you can only exchange, not subtract. Subtraction requires energy investment, which is why we need to go to such great lengths to make RODI water. When you soften water, you're usually exchanging calcium and magnesium for either sodium/potassium (water softening pillows, home water softeners) or protons that lower pH (some ion exchange resins, peat). You can see where this would be very limiting if you want to finely control your water conditions. That being said, there are relatively few circumstances where you need this kind of control.


Also, distiller water should have the vast majority of salts removed, including the carbonates that contribute to KH.

That makes sense. While playing chemist is fun, I would rather have a healthy, stable, and attractive tank, so I'll stick with the store-bought stuff and use my tap water for my mbunas.

 

[phin]

Actually (at least in my local) most of the vendors run 3 types. RO, DI, and carbon. Where most bottled spring water is only distilled or a combo of distilled and RO. Which is why I use the vendored water. It is the only way I can cut my gh/kh down.

I'll have to ask my LFS next time I'm in and see what he says. I used it before, I didn't have a KH test at the time, but the GH came in at 9. I don't know if that was a mistake on my part or not, but my tap water GH is 16, and they are on the same water as me. After doing a ~50% wc I had a GH of 12 and decided it wasn't worth the trouble to drop my GH by that little.

 

[phin]

.... When you soften water, you're usually exchanging calcium and magnesium for either sodium/potassium (water softening pillows, home water softeners) or protons that lower pH (some ion exchange resins, peat)....

On another note, would you agree that peat has more benefits to the aquarium than just adding protons to lower pH (assumed desirable)?

The humic acids in peat contain carboxylate and phenolate groups that allow humic acids to form chelate complexes with ions that plants need Mg, Fe, Ca, etc. that increases the bioavailability of these ions for plants? Isn't that the same principle that supplements advertise chelated iron? In addition, I would surmise that the chelating effect that is of benefit to plants would also protect them from any toxic metals present, in the same way water conditioners detoxify heavy metals.

 

[aqua_chem]

Yes, I agree with that statement. Humic acids have a well documented ability to chelate heavy metals. Chelated iron is actually advantageous for a different reason, but it is possible that chelated metals are more bioavailable. I can look this point up later after I get home. Diana Walstad holds humic acids in pretty high regards in many of her writings.