Quote:
Originally Posted by VaughnH
Bill, the reason to avoid big water changes when you are doing a no-CO2 tank is to avoid introducing CO2 with the water change, not other nutrients. Tap water usually has some CO2 dissolved in it, so adding half a tank of tap water adds considerable CO2. Then the CO2 dissipates and is used by the plants, bringing the tank back to under 3 ppm of CO2. Those peaks of CO2 followed by very low CO2 can trigger algae blooms.
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Please excuse my continuing confusion, but if you do EI with its 1/3 to 1/2 tank volume water change, aren't you causing the same CO2 spike and drop that could cause algae? Even with the injected CO2, these plants aren't going to need much in the way of nutrients with 1.5 WPG, particulary if they are low light, slow growing plants like crypts and anubias.
As Tom said, "Walstad-type" tanks shouldn't have have many water changes (for the reason you stated) and it would seem that would also extend to all low light tanks, even though they used injected CO2. Right?
But then Tom also said that he has kept low light tanks with and without CO2 injection and used EI without problems. So then maybe the warning not to make large water changes in "Walstad-type" tanks can safely be disregarded?
If that's true then I'm no longer confused, at least until the hard core Walstad-ites begin their rebuttals.
Bill