Aquatics Unlimited: Articles: Plants versus Algae
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Plants versus Algae

for the week of 12/30/99

Part two of three on the green/brown/red slime/crud/hair that aquarists are forever battling.

Do live plants cause algae? Nope; in fact, quite the opposite. Live healthy plants consume the CO2, N, P and K that algae also require for survival. If started early and properly maintained, live plants can outcompete the algae for these nutrients, and greatly reduce algae growth.

Why do some people experience algae blooms after adding live plants? First, live plants likely have a tiny amount of algae on them, and if conditions are right, that algae may grow rapidly. But the bigger problem is dying plants or leaves, which not only fail to consume algae nutrients, but actually provide them as they decompose.

So what's the trick? Success depends on a flourishing population of healthy plants, so either proper conditions must be arranged for the desired plants, or plants must be chosen that will thrive under the existing conditions. This could mean either extra lighting, CO2 and nutrients for a thick growth in a "natural" aquarium, or selecting a few easy plants for the fish tank with normal lighting. Any plants or even leaves that appear to be composing should be removed promptly.

Can you have too many plants? In a way, yes. If the plant population eventually grows to the point where it constantly consumes all of any one of the basic requirements (most often Nitrogen), it no longer continues to thrive. Algae then has a chance to become established as nutrients become available that weakened plants are not using, and even more nutrients become available as dying plants decay. The simplest way to avoid this is to occasionally thin out some of the plants by pruning stem plants like Anacharis or removing rooted plants like Vallisneria.

"Tip of the week" appeared regularly in 1999 and 2000.

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