Help me pick a ph. (co2 injected tank)

[sherry]

I have FINALLY begun injecting co2 into my planted tank.

My kh/gh are both 2.

I am trying to do this without additional buffering if I can since I have softwater fish/plants.

Oh and running my controller without the co2 plugged in told me that my co2 is 6.5 in the morning (after the plants have been on lights out all night) and 6.7 in the evening.

I calculate that by running the controller at 6.4 I am adding 12 ppm of co2 for a total of 16 ppm.. The charts show more .. but they also seem to say I have 13 ppm naturally which makes little sense.. so I think they must be at least 8 ppm off from other acids in the tank. Instead of reading the chart exactly I am instead subtracting 8pmm from the final result.. Oh and a great chart with moveable rulers ... http://www.dennerle.de/HG07UG07.htm

So, in a tank with Apisto cacs, soon to be evicted rummynose tetras, soon to be added pencil fish, otos, a couple of bristlenose plecos and some featherfin rainbows, how low a ph can I maintain?

I'd love to get the co2 concnetrations at 6.3 or 6.2 if that is okay for the fish. The charts say 6.3 gives me a perfect 30 ppm of co2, but if I subtract 8 ppm from the total.. the ideal co2 levels seem to fall at ph 6.2.

I can buffer and bring the co2 concentrations UP, but since the co2 doesn't seem to be bouncing around any, I'd like to try to do this without additional buffering.. I can be talked out of this if I am taking too great a risk.

thanks!!!

 

[malkore]

a dKh of 2 should give a natural pH of 7.2 (roughly.

If your rested pH is lower than 7.0, then you have something else (acid, other chemicals) lowering your pH, and rendering the pH/Kh chart invalid.

 

[sherry]

I understand that.. Malkore.

I need to know two things.

1- can I use a "differential number".. assume the first number without injection is invalid.. but that the CHANGE in ph is valid.?. there fore.. if the chart says 12 when it should say 4 ppm.. can I assume the rest of the numbers are merely 8 ppm too high?


Next, How low can I set the PH without hurting the fish.

pencils, tetras,apisto cacs and bristlenose plecos.

 

[czcz]

if the chart says 12 when it should say 4 ppm.. can I assume the rest of the numbers are merely 8 ppm too high?

I am no expert on pH, but since you are playing with an exponential relationship, that assumption is incorrect. I think the CO2/KH/pH chart will be useless for your tank, as Malkore said.

I recall published measurements from some of Takashi Amano's tanks (with fish) that showed extremely low pH. His substrate drops pH. I think many of your SA fish see lower than pH 6.2 in nature. I do not know if this is true of the other fish or inverts. If anything, I think it is the stability you have to worry about, and luckily you have a pH controller to worry for you.

If I were you, I would gradually lower pH to 6.2 while observing my animals. I would dose Excel if I observed carbon deficiency in plant or algae growth. If this became cost prohibitive, and I am certain the issue is carbon and my fish are fine, I would weigh my options. I would be considering dropping pH past 6.2 while continuing observation, raising KH, or perhaps changing my fish stock to animals I know see very acidic pH in nature. I would probably continue to drop pH by small increments.

That said, remember, not an expert. FWIW, my pH in my softwater tank is below 6.2, I have DIY CO2 as stable as I can (which is still unstable and will swing pH by at least .2), and my plan is to slowly aclimate any fish I add. I feel confident this will work, but only because of what I have seen online and read about in other tanks. I'll post when I do it, though. HTH

 

[Wizzard~Of~Ozz]

I would put some tank water in a small bottle, shake it for a while, then let it sit for an hour and measure the PH, this will be the base PH with little to no Co2. Then you know if it's your substrate (I think Flourite is PH 6.2) or a natural high Co2 level. from there I would assume(I don't know for sure, this is just a logical assumption) that PH is Co2 0, find that on the chart for your equivilent PH level (I think 7.2 was mentioned). Calculate the difference you want to drive it (say, PH 6.5 for XX ppm Co2), subtract .7 from your base ph level and that should be the correct amount.

Let say your standing PH is 6.7 with 0 Co2, you would have to take it down to 6.0 which may be too low for some of your fish, then you have to decide whether you want to increase the KH by 1 or 2 degree's to allow a more nuetral PH.

The Co2 level isn't linear, (not going to be .8 too low for all levels), but using PH as your scale should take you relatively close.

As a note, in my reading I found somethign that said

PH, KH and Co2 are a triangle, what affects 1, affects the other to balance.

so with that being said, you very low PH will drive up your Co2 or drive down your KH to compensate.

Most calcs are useless lower then KH 3 anyway (and the inherint instability is evidence of why) so I think czcz is correct, try PH 6.2, see how it does for your plants and fish. increasing the buffer is the only way to truely make it calculatable.

 

[sherry]

Someone else made another point that changed my mind about buffering.. He mentioned that just because mykit seems to say kh2, it could actually be lower.. somewhere between 1 and 2, which would also account for the low ph levels.

So I decided to put a tablespoon of crushed coral in the filter to see how that works out.. This way maybe if I stabilize my kh a bit, the ph levels will make more sense and the charts might just work.

aside from some driftwood (and not huge pieces) I don't have anything that should push ph down. so the idea that my kh is actually below 2 made sense.

I'm going ot tyr to keep ph at 6.4 for now. I don't mind supplementing a little excel. The excel was workign well. I am just trying to make the system work even better.

 

[BrianNY]

JMO but I think you're trying too hard to refine the pH number sherry. The fish you mention will do just fine with a pH above 7 as long as it's not jumping all over the place. The best thing to do IMO is buffer your water.

 

[czcz]

Ozz,

You're right though about pH drop when KH and CO2 are constant according to the standard formula. In my mind it is the fluctuating initial pH (per change in pH from 6.5 to 6.7 with no injection) that screws it up in this applied example.

In case anybody wants it for their spreadsheet or something, CO2 = 3*dKH*10^(7-pH) is pH = 7.48 + log(dKH/CO2)

 

[sherry]

buffering underway.. .I'm told it will be a few days before I actually know the results of the amount of cc I put in...

hoping to keep the kh near 3 tho.. cz, any idea how the tonina will fare at that level?

oh, and cz, how is your hillstream doing? I lost my three during the last mini-disaster and have decided NOT to replace them until I can set up a river tank for them. I love the fish tho and will miss them.

 

[czcz]

I would not venture to predict how your Tonina will grow, but as before, I don't think 3 dKH is too high, based on the parameters of others. I have only tried it in two enviornments -- KH 5.5-6, pH 6.6-6.8 and KH 2 pH <6.2 -- and only one did well. While more advanced growers have had difficulty with it at high KH, and it is a plant I feel will continue to teach me for a long time, I still find it hard to believe that 1 dKH would make or break a plant. That said, I am becoming happier with my softwater tank, and am afraid to raise KH by one degree to see what would happen How is your Tonina doing?

Aside, I think it will be hard to raise KH by one degree with CC, and if by chance it's the easiest method, KH climbs a little past your target, the fish stay great, and Tonina does not thrive, I think valuing the fish more than the plants is admirable. I suspect everybody has had at least one plant that doesn't like their tank FWIW, I will not stock my softwater project until I am done messing with stuff, and ultimately may find it does best as a plant and snail-only tank.

My Hillie is in the great river in the sky. I had him for less than a year, and he spent the last eight months in the river tank. He passed about a month ago, maybe two. Maybe we are going through similar things with this great fish: I want another, and love hillstreams, but am not sure if I should get another, as I feel guilty for wanting a wild caught fish with such specific requirements. One of my LFS gets them in occassionally and their stock drops faster than I think they could possibly be selling them, so I consider "rescuing" one from time to time, and then of course I feel guilty again. Its just too soon for me

I was sorry to read about your losses. IIRC, Martin sang you a song on The Loach Forum, and I'll bet with his guidance your river tank will be sweet. You are putting together and planning very interesting tanks, and I enjoy reading about them.

Joe