Discouraging Algae in the Planted Aquarium
by Martin Sendera
If you have attended any WAKO meetings recently, you may have noticed an increased interest in plants up for auction. I know I have. The last auction even saw Java moss going for several dollars a bag! I'll have to bring a few bags of it to future meetings. Recent meetings have also had more discussions about tips on growing plants and plants problems, especially problems with algae. Why can many people in the club successfully keep delicate, finicky killies yet fail with aquatic plants? I feel it must be a lack of understanding of plant fundamentals.
This is not going to be a primer on lighting for the planted aquarium (perhaps in the future). Everybody knows plants need light. So you supply plenty of light to your aquarium and expect your plants to do well. Most do OK, but the algae does better. Why? Too much light? Wrong type of light? Bad karma?
No, you are simply meeting the needs of the algae better than that of the plants that you want to grow. Reducing the light levels is only an option for ferns, mosses, crypts and other "shade tolerant" plants, but even these will do better with more light and it doesn't really get to the root of the problem anyway.
The real solution is improved water quality. Higher aquatic plants have different needs than those of algae. Higher plants do well in nutrient poor water while algae does better in nutrient rich environments. I'm not talking about trace elements or vitamins, though they need to be present in small amounts for any type of plants to thrive. I'm referring to the basic metabolic by-products such as nitrates and phosphates. When these accumulate, algae thrive and higher plant growth is diminished. High nitrate levels can even increase the light requirements of higher plants.
The problem for most killi-keepers is that the levels of these plant nutrients are unknown and eventually get too high. Algae growth can only be limited if either phosphates or nitrates or both are kept at very low levels. Phosphates need to be kept as low as possible, no more than 0.1 - 0.2 PPM. Any higher and algae growth will be stimulated. If it gets above ~1 PPM, you'll have real trouble. Nitrates are less critical, but should be kept down around 10 PPM.
You'll need to monitor at least the phosphate levels, and optionally the nitrates, with a test kit that is accurate at these low levels. I found the test kits from Red Sea Fish pHarm Ltd. work well in this range, are easy to use, and are relatively inexpensive. LaMotte has an even better line of test kits, but they are expensive. If you want to try some other test kits, just make sure they are made to work with freshwater; some are for saltwater only.
Note that phosphate levels need to be kept about 100 times lower than the nitrate levels and thus are the more critical of the two. Fortunately phosphates are easier to control. The easiest way to control phosphates is to have many plants and just a few fish in your tank. That's easier said than done. That big planted tank with almost no fish in it is hard to ignore! So you add more fish to it and promise yourself you'll do more frequent water changes to compensate for the higher bioload. Right. This also assumes that the water you use to make these water changes with has very low levels of phosphates/nitrates. That's not always true. EPA standards allow higher levels of these than you want for a planted aquarium. Both nitrate and phosphate levels can be significant if you live in farm country, which is most of Wisconsin. R.O. units will significantly reduce these nutrients. I use 3/4 R.O. water mixed with 1/4 tap water even though lake Michigan water is very good in this regard.
To keep phosphate levels in the tank low I add phosphate adsorbent media to the power filter. This keeps the levels low even when I slack off on water changes. There are adsorbent for nitrates as well, but these are a waste of money. If the nitrates are building up, you need to do more or larger water changes as well as clean the filter and gravel more frequently. I find that nitrate levels are the best indictor of proper tank maintenance regardless of whether it is set up as a plant tank or not.
So much for testing for things you don't want (in excess). The one element that you do want in the planted aquarium but is often too low is iron. Without adequate iron your plants will turn yellow even with plenty of light. Well water often has plenty of iron and you may not need to add any to the tank. All setups are different.
Many aquarium plant fertilizers contain iron but you can only guess as to how much you really need to add. You need to test to know if there is adequate iron. I tested for iron frequently when I first set up my plant tank and later only occasionally. I add enough fertilizer (usually Seachem) with each water change to register about 1 PPM.
Testing again just before the next water change should show some iron still present. If you can't detect any iron, add more fertilizer between water changes until you always have 0.1 - 1.0 PPM iron present. Any more is probably just wasted.
Note: cheap fertilizers may not contain EDTA which keeps the iron in solution and thus available for the plants to utilize. They cost less but you need to use more of them. You get what you pay for.
I set up a tank almost 10 years ago primarily as a plant tank. It has had every type of freshwater algae known to science plus a few that I should have saved some samples of for experts to study. All have disappeared or greatly diminished when the water quality improved. Slacking off on aquarium maintenance would inevitably bring on a new bout of algae problems. Testing is the only way to "nip these problems in the bud " (sorry, I can't help myself ).
Good luck with your plants!