help!?! with pH fluctuations please (planted tank)

[frog girl]

I have a DIY CO2 with plants in a 60 gallon (about) tank. My hardness is 10 dKH. I have 4 75 watt compact flourescent spiral daylight bulbs. The plants are producing oxygen like crazy but my pH keeps going down. In the last 3 days from 7 to 6.4. Today from 6.4 to 6.2.

Shouldn't the CaCO3 be buffering my pH??

Isn't there a saturation point for CO2 or will it just keep making more carbonic acid & my pH keep going down.

For now I have turned off my CO2 diffuser so the fish won't die of shock but I would like to keep it going so my plants will do their thing.

Can anyone explain whats going on?? What advice would you offer??

 

[BrianNY]

It's likely that too much CO2 is driving the pH down. How are you controlling the CO2 rate? A pressurized system with a pH controller would help.

 

[frog girl]

I am not currently using a controller. I know a pressurized system would help & a pH controller but I'm afraid I can't afford one just now.

My system is pressurized in a sense because it takes quite a bit of pressure built up in the bottle to actually get a bubble of CO2 down to where it is dispersed. My system is simple its just a pump with a cut in half plastic bottle on the end. The CO2 bubbles into the bottle which is placed horizontally & the pump runs water under the trapped CO2. I can change the rate of the pump which would decrease the rate at which CO2 is dissolved into the water & or put a tube in that would only allow the CO2 to build up to a certain level in the bottle. Or if I put my rig further down in the water column it would take more pressure in the bottle to get the CO2 to the bottom.

What I really need to know is how much my plants need because I am clearly providing them with an over abundance. I can just play with it until I get it about right . . . any DIYers out there that deal with this problem??

So CO2 doesn't saturate like O2???

If it did I could use the level in the diffuser bottle as a measure of when I was providing too much . . .

 

[youronlysin]

I dont think you necessarily need to get your co2 diffuser close to the bottom of the tank for maximum efficieny. I'll bet you could use less CO2 if you got your diffuser next to a source of moderate to strong water flow. Im not quite sure what you mean by saturation...the oxygen transfer in your tank (not including plants) occurs through stimulation of the waters surface near the atmosphere. Bubbles dont really oxygenate the water, they merely break the tension at the surface of the water so that atmosheric oxygen can be diffused. Now with CO2, I think it is directly diffused into the water as it is introduced. The longer the bubble is in contact with the water, the more CO2 is absorbed by the water. I know there is a lot more science to it than I can provide an answer to, but I think you should try to maximize the efficiency of your system, rather than increase the CO2 pressure or level. Last I checked, bubble counters werent too expensive. That might help you get a better idea of how much CO2 you need to use.

 

[frog girl]

I was thinking of the oxygen transfer through plants. I'm pretty sure if I remember my chemistry right that you can only dissolve so much of a gas in water (thus oxygen saturation). Maybe with CO2 since it produces carbonic acid with the water there isn't so much of a saturation point as with oxygen which I don't think ionizes at all in water.

I'm really trying decrease the efficiency of my CO2 rig because it is putting so much CO2 in the water that my pH is going down fast. I bet a bubble counter would help though (good suggestion). The problem will be how can I regulate the CO2 - thats why I thought of slowing down the pump so less would dissolve or maybe not letting so much CO2 build up in the bottle so not so much would dissolve.

Its sort of odd, from everything I have read DYI CO2 shouldn't be able to get too much into an aquarium as large as mine. Don't know whats up with that?? I'm only using 1 2 liter bottle.

 

[frog girl]

I was thinking of the oxygen transfer through plants. I'm pretty sure if I remember my chemistry right that you can only dissolve so much of a gas in water (thus oxygen saturation). Maybe with CO2 since it produces carbonic acid with the water there isn't so much of a saturation point as with oxygen which I don't think ionizes at all in water.

I'm really trying decrease the efficiency of my CO2 rig because it is putting so much CO2 in the water that my pH is going down fast. I bet a bubble counter would help though (good suggestion). The problem will be how can I regulate the CO2 - thats why I thought of slowing down the pump so less would dissolve or maybe not letting so much CO2 build up in the bottle so not so much would dissolve.

Its sort of odd, from everything I have read DYI CO2 shouldn't be able to get too much into an aquarium as large as mine. Don't know whats up with that?? I'm only using 1 2 liter bottle.

 

[frog girl]

why does my computer keep double posting??

 

[youronlysin]

That is strange that your KH was so high and your still having a ph issue. Maybe you can try to raise the KH even more by adding some crushed coral to the filter or something. Im not sure what to do to control your ph without a CO2 regulator.

 

[frog girl]

My pH didn't really become a problem unitl I reduced my KH by removing all my limestone rocks & replacing them with nonreactive ones. Then I have been doing slow water replacement & got my CO2 rig back up & running. I still have 10 dkH but apparently I just have a really efficient setup for dissolveing CO2.

I know I need a regulator . . . I need to read about them to see if there is a simpler solution (or if I can jury rig one). I really love the look of a healthy planted tank & would hate to give that up for lack of a regulator. I guess I could just go fishless :| .

 

[youronlysin]

What are you using to diffuse CO2?

 

[BASSNMAN]

You might try putting a t in your co2 line with a valve on the open end. This would let you bleed off some of the pressure and lower your co2 rate. Yor plants may be burning up the carbonates in your water. Try adding a teaspoon of baking soda and see if your ph stabilizes. I need to do this weekly to my tank.

 

[frog girl]

Its basically just a pump and I have attached a small plastic water bottle with a narrow neck to the outflow (the outflow & neck of the bottle are about the same & I stuck it on there with a washer. I cut the bottle in half lengthwise & I let the CO2 bubble into the half bottle with the pump on.

Its just a place to trap the CO2 with a water flow across the bottom of it. If the bottle fills up to much which it does regularly the gas just escapes to the surface.

I think I can slow down the reaction of the DIY CO2 generator by using flour instead of sugar. The yeast will take longer to metabolize the flour & this should mean less CO2 bubbling in (a slower reaction for a longer amount of time.

I can also increase the KH easily by putting some limestone back but do I really want it higher than 10-12 degrees for a planted tank??

 

[frog girl]

thanks Bass I will try that. So the plants can eat up my carbonates. I thought only a couple plants actually absorbed Ca through the water & I'm still getting a pretty high KH reading of 10 so they cant be to eaten up.