# Whats a good GH Target?



## Arana (22 Oct 2007)

My water straight from the tap is PH 8.0, KH 8 and GH 18, i have used Co2 to bring the PH down to 7 with gives me a nice concertration of Co2 for the plants but is GH18 a bit high for them?


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## Ed Seeley (22 Oct 2007)

Unless you're growing plants that need soft water you shouldn't really have any problems with 18dGH.

BTW you will probably be best to use CO2 to aim for 30ppm of CO2, rather than a specific pH as this will give you more stable CO2 levels.  pH is effected by so many other factors that can change it and could cause your CO2 levels to fluctuate if you alter the CO2 to maintain a steady pH.  Fluctuations in pH by CO2 seem to have absolutely no effect on the fish.


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## Arana (22 Oct 2007)

Thanks Eds, best to leave it alone then... i hsve adjusted my Co2 levels to give me about 25ppm hence the PH of 7 i'm not too concerned about the PH is this what you meant? would 30ppm be a safe level for a well stocked tank? i'm more than happy to turn it up a bit if it's safe.


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## Ed Seeley (22 Oct 2007)

Arana said:
			
		

> Thanks Eds, best to leave it alone then... i hsve adjusted my Co2 levels to give me about 25ppm hence the PH of 7 i'm not too concerned about the PH is this what you meant? would 30ppm be a safe level for a well stocked tank? i'm more than happy to turn it up a bit if it's safe.



No you can stick with 25ppm (How are you measuring this BTW, via a drop checker?  If so what Kh is the water in the drop checker?).

The reason lots of people have used 30ppm as a benchmark is if the KH of the water in the drop checker is 4dKH then when it turns a nice light green you have 30ppm CO2.  By adjusting the KH of the water in the drop checker then it will turn green at different CO2 levels.

What I was clumbsily    referring to was people who use a pH meter or monitor linked up to CO2 to keep the pH at a set level.  This can cause swings in CO2 levels if something else effects the pH.


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## Matt Holbrook-Bull (22 Oct 2007)

just to reiterate what Ed quite rightly said..

the ph in a tank can be altered by a large number of factors other than co2 content, this is why we started to use a drop checker in the first place, containing a lab tested KH solution, and not tank water.  4dKh was decided upon (by quite a few of us on the barr report) because it went green at the desired 30ppm (+- 10ppm).

Arana  yeah 30ppm is fine, as would be higher than that to be honest.. just make sure you have adequate surface agitation and dont add co2 when the lights are off. (although there are mixed theories still about that).  Gas damage to fish isnt caused by co2, its caused by LACK of O2, adding co2 doesnt replace O2.

basically. test kits are far too inaccurate measure co2 with any certainty, even if we calibrate them to the best of our home based equipment.  This is where the Estimative Index really is worth its weight.. once your sure your ferts are in order, you can throw every test kit away, and start thinking about scaping, which is why we do this in the first place


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## Arana (22 Oct 2007)

Thank you both   i used a co2/KH chart to get the Co2 level, i will now go and add the drop checker that came with the JBL kit  
I am intending to leave the Co2 on 24/7 if possible to promote stable water peramiters and maiintain a healthy supply of Co2 for when the lights come on, if nessecery i will increase surface movement and/or move fish out to one of my other tanks to try and strike a balance. At the moment everything is pearling nicely with 180w over approx 240L (after displacement) Full EI starts when my ferts arrive from AE 8)  at the moment i'm dosing daily with api leaf zone.


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## Matt Holbrook-Bull (22 Oct 2007)

you can buy a 4dKH solution from aqua essentials, its expensive, but itll last an eternity! youll need that or to make one if you have digital scales and a steady hand by putting bicarb in distilled water.. tank water or tap water wont do you.. even tap water varies a long way from its water report.

 anyway, George is another who adds co2 24/7, so 2 schools of thought


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## Arana (22 Oct 2007)

Thanks again Matt, Ive just been to AE and ordered a pretty glass drop checker and some 4dkh solution... Happy Days


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## George Farmer (22 Oct 2007)

Frolicsome_Flora said:
			
		

> anyway, George is another who adds co2 24/7, so 2 schools of thought



Don't listen to him (George), Arana.  He knows nothing about plants...


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## Dave Spencer (22 Oct 2007)

Frolicsome_Flora said:
			
		

> Gas damage to fish isnt caused by co2, its caused by LACK of O2, adding co2 doesnt replace O2.



It is possible to kill your fauna with too much CO2. Whilst the CO2 does not displace the O2 levels, fish need the CO2 concentration in the water to be lower than their metabolic levels, otherwise they can`t rid their bodies of waste CO2.
 
Dave.


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