There's a lot to like about iwagumi aquascapes. Their simplicity is calming and beautiful and there's something special about watching a school of fish hover over a "field" of grass. Starting your own iwagumi aquascape, especially your first, is likely to lead to the exact opposite feelings: lots of pulling out of one's own hair and frustration as your aquascape is consumed by every algae known to man. Why? Well iwagumi aquascapes usually rely on only 1 or 2 species of plants, usually carpeting plants like dwarf hairgrass or HC, which don't grow particularly fast or soak up a lot of nutrients. Let's imagine a typical beginner mistake starting up an iwagumi aquascape.
When you first start an iwagumi, chances are you have some rocks, and a species or two of carpeting plants. You probably have a CO2 system of some sort, and pretty powerful lights and a fertilizing schedule. The aquarium probably looks pretty barren, aside from a few sprigs of plants strategically placed. Fast forward 3 weeks and you probably have a mess of algae that has covered your rocks, plants, and even substrate, suffocating the remaining carpeting plants into submission.
What happened? You created a perfect environment for algea. When you set up a tank, it's critical for your aquatic plants to establish a dominance, soaking up all the nutrients they can. If you don't have enough plants, algae moves in and will smother everything, thriving on the excess nutrients your plants aren't using.
So how can you avoid this when you set up your first iwagumi aquascape? The key is fast growing stem or floating plants. Add as much of these as you can, without shading out the carpeting plants. They are excellent at soaking up excess nutrients and some even release chemicals that retard the growth of algae (called allelochemicals). They don't have to disrupt your pefectly planned iwagumi layout, simply float them in your aquarium for the first few weeks, or until the carpeting plants have a chance to take hold and spread. Also, hold back a bit on fertilizing until your plants really start growing, and fertilize in proportion to the amount of plants you have in the aquarium. Gradually up the fertilizing, keeping track of algae and reducing it if you see the algae starting to crop up. This helps swing the balance in favor of your aquatic plants, and algae won't have as much of a chance to gain a foothold.
Some plants that work particularly well at keeping algae at bay in the early weeks of a newly set up aquarium are Hornwort, any hygrophila species, or any floating plant (although these can quickly become a pain to get rid of since they grow so quickly and tend to hide in everything--I'm looking at you duckweed!).
If algae does get out of balance, the best thing to do is reduce your lighting period, reduce fertilizer dosing if you are dosing too much, make sure your CO2 is steady and wait. As long as everything is balanced, your plants should be able to outcompete the algae and your iwagumi will be back on track.
Good luck!
*Photo by Mikhail Sharonin of Russia, who placed #435 in this year's IAPLC contest
