Ph and CO2 - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 8 Old 01-23-2012, 01:41 PM Thread Starter
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Ph and CO2

I have made the transition from years of plastic plants in my freshwater tank to a fully planted tank. I have also stopped using carbon, Phoszorb and Nitrazorb filters, going instead with just foam sponges and Biomax. I have a Fluval canister filter system with an inline heater (I keep the temp 72-74 F). I have no more algae problems. My plants seem to do OK and grow slowly. I trim the brown leaves and stems that develop. Java moss is doing well. I have 4 clown loaches, 5 cardinal tetras, 4 red eye tetras and 3 yellow fin tetras and 3 other tetras that look copper on their fins. All fish do well.

My tank is 40 gallons. I do 50% water changes every week. I add Fluorish every 3 days.

As section of my tank has a floating plant to provide some partial shade (the tetras love hiding out in it).

My tank runs consistent parameters when I test the day I do a water change:

pH 6.0 - 6.2
GH 6-7
KH 1
NH3 2
Nitrite 0
Nitrate 5
Phos 0.5

I vacuum the gravel once a month.

I have read that plants like a pH higher than my tank's pH. Is this true?

Also, I don't measure the CO2 in my tank. Should I be doing so? If so, then is it best to do so during the day or at night? I have the tank's light running ~10 hours on average each day.

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post #2 of 8 Old 01-23-2012, 02:02 PM
plants will be fine at that pH generally. If you ever reach very dense fast growth you may just find that you need magnesium and calcium addition for the plants.

As far as CO2 you don't need to monitor it unless you are adding it. On a tank that size only a pressurized system will need to be monitored.

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post #3 of 8 Old 01-23-2012, 02:19 PM Thread Starter
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Thanks for the info!

Does it matter how fast I set the filtration? Does that affect the CO2 level at all?
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post #4 of 8 Old 01-23-2012, 02:27 PM
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Not so much how fast it is but how much it disrupts the surface of the water. The more surface agitation there is, the more gas exchange there it.

Measuring CO2, if you are running pressurized, get a drop checker. That will give you a guide as to how much CO2 is dissolved in the water. As long as the color is in the green, you are good. Start dipping down into the more yellowish color, it could be too much. Not for the plants but for the fish.
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post #5 of 8 Old 01-23-2012, 02:32 PM Thread Starter
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Thanks again. I have not been adding any CO2 to my tank. I can get a CO2 test kit and check the status of the CO2 level.
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post #6 of 8 Old 01-23-2012, 02:44 PM
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Opps...for some reason I thought I read you were adding CO2. If not, really no need to test. Plants do like lots of CO2 and without adding it, you are getting a limited amount. If the plants are healthy then there isn't anything to worry about. If you want them to grow faster, add CO2, more light, and ferts. If you are happy with the growth rate, keep it as is.
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post #7 of 8 Old 01-23-2012, 08:15 PM
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Agree with what has been posted. One thing to add on the filter question, and that is that water flow can impact CO2 assimilation by plants. So while the flow in the tank will not deplete CO2 (surface disturbance will as was already mentioned), too fast a water current makes it hard for plants to grab the CO2. The increase in oxygen is also detrimental.

This came up in another thread recently; rather than repeat, here's the link, my comments are in post #4:


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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post #8 of 8 Old 01-24-2012, 07:53 AM
Thanks for giving the very useful information. I really liked it.
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