Hard water planted tank question - The Planted Tank Forum
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post #1 of 7 (permalink) Old 02-10-2013, 07:31 AM Thread Starter
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Hard water planted tank question

I was considering using my natural hard tap water on a 55 gallon planted tank. My question is: My Gh is around 17, Kh 7, TDS 530, Ca 71 mg, Cl 91mg/L, Na99mg/L, Flouride .76mg/L, Ph 8.0. I know this is not pretty. All my planted tanks I usually run 100% remineralized r/o & do well.
Can I grow some plants if all other things are better? Say 6500k bulbs, dry ferts, Flourite substrate, canister filter. I would stock with sword tails & mollies which like hard water, But the question is , is the sodium too high & what about the flouride with the fish & plants. The only reason I want to try this is to save some money & water. I know I can grow plants well in R/O water with pressurized CO2 , but to try it without Co2 all other things being equal would be an interesting challenge + I really would like to see sword tails & mollies again in my home.
The big show stopper to me could be the sodium, plants do not like sodium. Is the reported 99mg too high & my plants would melt & die???? Any ideas , should I forget this idea or does somebody have success stories they could tell me with similar conditions???
I figured hard water plants would go after the bicarbonates & Co2 would not be necessarY. Maybe CO2 could be used for more diversity in plant species as well as another option. But there maybe just too much sodium to pull this off. Any suggestions or experiences would be great thanks.
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post #2 of 7 (permalink) Old 02-10-2013, 10:19 AM
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I know from experience that algae is a nightmare if you apply high light to alkaline tanks, because they are better with bicarbonates.
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post #3 of 7 (permalink) Old 02-10-2013, 01:08 PM
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My first planted tank was filled with tap water that had a ph of 8.4. I had to spot treat algae here and there, but it was never overrun and the plants did fine. I didn't have any finicky species though.
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post #4 of 7 (permalink) Old 02-10-2013, 01:31 PM
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You shouldn't have any problems. Your water is similar to mine (TDS 587, sodium 118, pH 7.9, Ca 73) and I am growing Vals and several varieties of swords.
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post #5 of 7 (permalink) Old 02-11-2013, 05:42 AM Thread Starter
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Thanks all. Sounds a little encouraging. I looked up more on hard water plants & it seems the amount off species is less than soft water. That would not be a problem for me. I would be happy with 3 or 4 species as long as I could control the algae. Not sure if I would dare run a couple of soft water plants in as well CO2 or not they would probably grow better emergent.
I am still not sure at what ph or alkaline point the Free CO2 gas would turn into bicarbonates if I ran pressurized CO2. That would be another interesting experiment. Right now I am leaning on trying a straight up hard water tank without pressurized Co2. How much difference would it make at higher Ph levels???? How many watts should I run with say T-8s with 6500k bulbs on a 55 gal in this application? I have the soft water tanks down well but the hard water tanks are a whole other world for me.
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post #6 of 7 (permalink) Old 02-11-2013, 02:27 PM
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At pH 6.37 and below, most CO2 would be carbonic acid; between 6.37 and 10.3, most would exist as bicarbonate, and above 10.3 it would be mostly carbonate.

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post #7 of 7 (permalink) Old 02-12-2013, 07:26 AM Thread Starter
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So, is it safe to say that Co2 gas in water is carbonic acid if the ph is above 6.37? And it will react similar as it does in softer water with a lower ph ,but you will need more of it?? Thanks for reply mark.
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