Aquarium Decoration (Rocks, Plants and Substrates) • Rock setup and algae

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Re: Rock setup and algae

Postby BC in SK » Sun May 10, 2020 6:27 pm

shiftyfox wrote: As you mentioned algae are plants and produce oxygen during the day. But at night the situation reverses and the algae consume oxygen. With a heavy algae infestation the oxygen can drop into dangerous ranges at night and threaten the life in the aquarium.

Plants and algae consume oxygen both night and day; though they only produce oxygen when there is sufficient light. There is a net gain in oxygen levels as they will produce far more oxygen in a day, then they consume in a day. Given the same biomass, algae use no more oxygen then plants do. If this really were an issue, it would be heavily planted tanks that could be deadly for fish at night time as the amount of biomass (and hence the amount of respiration) is many, many times what amount of algae could ever be grown in a typical aquarium. Again, it is dying and rotting algae that could potentially be an issue in terms of robbing oxygen......and that is the very same thing in a planted tank, as well. If a plant matter dies and starts to break down, this process will consume oxygen.
And if oxygen levels are ever an issue, all the more reason to keep the lights on a little longer so that the plant/algae contiue to produce oxygen for a longer span of time.
shiftyfox wrote:If the CO2 content in the water is no longer sufficient, algae are able to dissolve the CO2 out of the carbonate hardness (KH). The result is a decrease of this important water parameter which leads to an unstable pH level. The pH level drops significantly at night (to values as low as 4) and rises during the day to far too high values (up to values over 10), and this can mean the death of the fish.

First of all, in a tank with fish producing Co2, how algae with it's very low nutrient demands is going to run out of carbon, is more then unlikely. And yes, SOME algae can sometimes utilize alternate carbon sources(organic waste/breakdown or carbonates) but with any amount of water change, the notion that algae will make even the smallest dent in the KH of an aquarium is pretty hard to believe. pH4 and pH10 are virtually unheard of in an aquarium, let alone such an extreme swing from night to day. There are natural environments where this does occur in the dry season, but it's not only to do with algae, nor really anything to do with a glass box. I have/had tanks with considerably more algae growth then the OP. There is zero change in pH (always pH8) regardless of what I do.
BC in SK
Joined: Sat Aug 11, 2012 1:06 pm
Location: canada

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