Q. A number of people on the Aquatic Plants Digest (APD) list have been discussing green water problems during the run-in period on a new tank. Several people have suggested that we ought to ask you how you “run in” a new aquarium, and how your run-in strategy compares to your final trace element and fertilizer dosing levels. Several of the APD regulars have offered the opinion that green water flourishes in a nitrogen-limited environment. What’s your opinion?
A. I use a laterite-based substrate mixed according to the directions it comes with (Dupla laterite is my favorite, although the others work, too). I mix the laterite into the bottom one-third to half of the gravel. I want the substrate to be at least 3 inches deep in total, with a grain size of about 1 millimeter (3 millimeters max).
I know I’ve previously talked about soil substrates and about potting plants with soil, but this is not a good place for the novice aquatic gardener to start. Start with the safest route to success, and then build on that as you gain experience. The species that do best in a newly set up tank will not require soil, and by leaving soil out of the tank you will avoid any possible leaching of nutrients into the water column.
I always use between 2 to 3 watts per gallon of appropriate fluorescent light. At 2 watts per gallon I might not use supplemental CO2, depending on water chemistry, while at 3 watts per gallon I definitely use it.
I plant heavily at the outset, and make sure that at least 75 percent of the footprint of the tank is planted. Of those plants, at least 60 percent should be fast-growing species. Some of my favorite run-in plants are water sprite, water wisteria, Hygrophila polysperma, H. angustifolia, Rotala rotundifolia, Vallisneria and Salvinia. But if you have plants you know do better in your home water conditions, use those.
I run the filter media for at least a week on an established tank before transferring it to the new tank. If you don’t own another tank (it doesn’t have to be a planted tank) and don’t know someone who can do this for you, ask your local aquarium store to do it. Most will oblige. By doing this, you start your tank with a completely functional biofilter. This method is even more useful if you are setting up a non-planted tank. You can completely avoid all the problems collectively known as “new tank syndrome.”
After the tank is set up, this is my schedule for the first month.
Week 1: Run the tank, set up with all equipment (including your now active filter material) and fully planted, but with no fish. This gives the plants a chance to get their roots established before they are disturbed by fish. They will also have settled in enough to be able to start extracting nutrients from the system at this point.
Week 2: Add an appropriate number of algae-eating animals. My personal picks are Siamese algae eaters (Crossocheilus siamensis) and Otocinclus sp. Use a good-size school of otos. Other good options are livebearers of various types, particularly platys and goodeids, and some Ancistrus sp. “Glass” or “grass” shrimp will also eat algae, but you’ll need a lot of them. Do not feed them during this period!
Week 3: Do nothing.
Week 4: Do the first 25-percent water change and start using a good trace element supplement. My personal favorite is Tropica Mastergrow, but there are a number of other trace element supplements on the market these days. If you’re starting from scratch and don’t have a good feel for how much fertilizer you’re likely to need, start by using no more than half the manufacturer’s recommended dosage, and work up from there based on the response of your plants.
At this point, there should be no algae problem in the tank. If the tank is looking good, you can start stocking the tank with fish over a period of time. Light feeding of the fish and regular water changes should also commence. On my tanks, I stock a little more heavily and do weekly 25- to 30-percent water changes. When I am advising others, and particularly when I’m setting up classroom tanks, I have them stock the tank more lightly (about 1 inch of small fish per 2 gallons of water), and do 25-percent water changes every two weeks. The important thing to remember is that the water changes will have to keep up with the fish and food load in the tank. The more fish and feeding, the more water to change on a regular basis.
If there is an algae problem, it could be because there has been a large die-off of plants, either because they were unsuitable species or because they were in poor health when placed in the tank. In either case, do not add more fish. As plant leaves die, they release the nutrients in their tissues back into the water. You don’t want to add more at this point.
Manually remove as much algae as possible as it appears. Remove all dying plant material as soon as you see it. Install sponge prefilters on filter intakes, and rinse no less often than every 48 hours to prevent plant material from breaking down within the tank. Do water changes no less often than weekly (and no less than 25 percent per change) until the algae problem is under control. You can go as high as 50 percent daily for a few days if absolutely necessary. I would also not add trace element supplements until this initial algae problem is brought under control.
The best way to avoid this type of initial die-off problem is to buy local aquarium-grown stock that has come from similar water conditions and hasn’t withstood the trauma of shipping. This means the best place to buy plants is often your local aquarium society auction. The best plants are the most common (rapid growers) and should be quite inexpensive.
As time goes on and the tank remains stable and in good condition, you can slowly cut back these rapid growing species and replace them with more choice, slower-growing “specimen” plants if you choose. This is when it sometimes makes sense to order from a mail-order house if you can’t get what you want locally. At the same time, you can pass some of your “weeds” along to someone else who needs to get started!
We talk about “green water” as if it’s one organism. It’s not. There are many, many species of unicellular suspended algae. I’m not at all convinced that they all have exactly the same needs. Some may have an advantage in a nitrogen-limited environment, whereas others may not. In my experience, green water is usually brought on by some nutrient imbalance in the tank, often an excess of phosphate. Sometimes an excess of phosphate can be traced to a nitrogen deficiency, but it is more likely to be a sign of overfeeding, too heavy a fish load or accidental introduction.
The water in all of my tanks is almost always nitrogen limited. I never have any measurable nitrate, and I almost always have at least trace levels of phosphate. This does not necessarily mean, however, that the plants are nitrogen-limited. If there is nitrogen available through the substrate, it doesn’t matter whether the water contains measurable levels of nitrate or not, as long as you are growing rooted plants. I sometimes supplement nitrogen in mature tanks if the plants show signs that they need it, but I do it via solid fertilizers in the substrate.
I do not believe that you can tell whether a tank is nitrogen limited by the use of a test kit. Healthy growing plants are very good at scavenging even small amounts of ammonium. It is only if there is more ammonium available than the plants can use that you will get any nitrate buildup. I prefer to watch my plants. If the plants don’t show signs of nitrogen deficiency, I don’t worry.
I would strongly urge caution before adding any macronutrients to a fairly new tank (less than three months old). It takes quite a while for plants to settle in, use up their reserves plus the nitrogen available to them within the system from fish waste, etc. Even in older tanks, it is typically only strongly lit, CO2-supplemented tanks with very high growth rates that eventually become nitrogen limited.