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Tufa limestone error

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Maff

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I'm setting up a small 72 litre planted tank and read about inert rocks so I chose lava rock. Went to the pet shop and bought three large lumps of lava rock. Me not being a geologist and the owners of the pet shop not up on rocks either, they placed tufa limestone in with the lava rock by accident and I bought them. Cut a long story short, the tank has been planted two weeks in Fluval stratum with the rocks and a piece of drift wood. It's low tech, I inject a small amount of co2, about 5ppm and the plants are doing really, really well. In fact, they've took off and the PH is 7.4 and is stable right there.
My question is, in a few months time, I want to stock with fish and had planned on either 8-10 Harlequin rasboras or maybe 8-10 Tiger barbs but have I jumped out of their parameters?
If so, what single species would you put in?
Thanks
 
And how long would you leave it before you'd put fish in? What type of fish are less likely to rip up the plants?
 
pH isn’t as important as hardness, and the tufa rock will continually dissolve more carbonates into the water, increasing the KH. I’d replace them if you want to keep soft water fish.
You can add fish as soon as the filter has cycled.
 
How much limestone, or what I'm wondering about in asking this, is how much it might/could dissolve enough to affect the water chemistry. What is the GH and KH of the source water?

BTW, the tank is not really large enough for Tiger Barbs, they are best in a 30 gallon/113 liter in a larger group.
 
It's hard water out of the tap, kh is 6. Gh is pretty high too so it won't dissolve calcium like soft water would. The limestone is not gassing off Atm.
 
The driftwood gassed off for the first 24 hours because of the tannic acid acting against the base water but now its absorbed the base water it's stopped gassing. I'm getting on average about 1 to 2cm of growth per plant a day with 5ppm co2 but my nitrates are at 40ppm out of the tap. Lot of nitrogen in there atm, too much for fish in fact at this junction in time.
 
It's ironic that I chose an active substrate like fluval which usually drops pH to between 6 and 6.8 depending on tap properties and ended up by accident putting in limestone which has counter acted it completely to a pH of 7.3. The fluval stratum is supposed to drop kh to zero but its at 3/4 and has been for 2 weeks. So I have got some buffering going on for when I inject co2 because it doesn't drop below 7.1ph during lights on of 8 hours. It really is growing plants quick but my fish choice has narrowed.
 
It's ironic that I chose an active substrate like fluval which usually drops pH to between 6 and 6.8 depending on tap properties and ended up by accident putting in limestone which has counter acted it completely to a pH of 7.3. The fluval stratum is supposed to drop kh to zero but its at 3/4 and has been for 2 weeks. So I have got some buffering going on for when I inject co2 because it doesn't drop below 7.1ph during lights on of 8 hours. It really is growing plants quick but my fish choice has narrowed.

This is reason enough not to use the Stratum or anything similar. Water chemistry is very involved, and adding anything that affects it is risky.

You didn't give the number for the GH. "Hard" is a subjective term and I have seen it applied to water that is actually very soft. You/we need to know the GH of the tap water.

Driftwood and other organic items will not have much effect on GH, KH and pH unless the GH and KH are very low. The GH/KH buffers pH. You really need the numbers.
 
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This is reason enoughnot to use the Stratum or anything similar. Water chemistry is very involved, and adding anything that affects it is risky.

You didn't give the number for the GH. "Hard" is a subjective term and I have seen it applied to water that is actually very soft. You/we need to know the GH of the tap water.

Driftwood and other organic items will not have much effect on GH, KH and pH unless the GH and KH are very low. The GH/KH buffers pH. You really need the numbers.
It's moderately hard at 200mg/l
 
It's moderately hard at 200mg/l

Yes. That equates to 11 dH (for those who prefer this unit). KH is given as 6, is that also ppm, or 6 dKH?
 
It comes out of the tap at 7.8ph and after 24 hours dechlorinated settles at 7.5 in my barrels so my other tanks are at 7.5. This tank is 7.3 and has been all along so it is buffering the effect of the fluval quite well. The fluval looses its acid buffering after about 12 months so that is when the calcium content of limestone could buffer my pH beyond 7.3 but I'm hoping it will only buffer it to 7.5. If it goes higher I'll balance it with new substrate when needed. One thing in my favour is water changes will be easier with a pH of 7.3 rather than 6.8. The plants are flourishing so far.
 
I think I'm going to go with harlequin rasboras when the time comes. Maybe a shoal of 12.
 

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