References

Setting Up A New Aquarium

The following discussion occurred between noted Aquatic Plant expert Karen Randall and Steve Dixon of San Francisco. It was published in Karen's "Sunken Gardens" column in Aquarium Fish Magazine in 1997.

Question: In addition to the discussion of green water on the Aquatic Plants Digest^*, I've gotten a lot of off-list E-mail from folks with similar problems. Green water must be a common problem, especially 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? I thought I would pass the comment along.

Answer: I use a laterite based substrate set up according to directions (Dupla laterite is my favorite, although the others work too) I mix the laterite into the bottom 1/3-1/2 of the gravel. I want the substrate to be at least 3" deep in total, with a grain size about 1mm (max. 3mm). I know I've 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 will do the most good 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 2-3 watts per gallon of good quality fluorescent light. At 2w/g I might not use supplemental CO2 depending on water chemistry, at 3w/g I definitely use it. I plant heavily at the outset, and make sure that at least 75% of the foot print of the tank is planted. Of those plants, at least 60% should be fast growing species. Some of my favorite run-in plants are water sprite, water wisteria, Hygrophila polysperma, H. angustifolia, Rotala rotundifolia, Valisneria and Salvinia. But if you have plants that you know do better in your home water conditions, use those.

I run the filter media to be used for at least a week on an established tank before transferring it to the new tank. If you don't own another tank (it does not 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 for you. Most will oblige. By doing this, you start your tank with a completely functional bacterial filter. By the way, this method is even more useful if you are setting up a non-planted tank. You can completely avoid all the problems collectively labelled "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 also will 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 (Chrossocheilus siamensis) and Otocinclus sp. Use a good sized school of Otos. Other good options are livebearers of various types, particularly Platies 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 during this period. Week 3: Do nothing
Week 4: Do the first 25% 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 as well. If you are starting from scratch, and don't have a good feel for how much fertilization you're likely to need, start by using no more than 1/2 the manufacturer's recommended dosage, and work up from there depending 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 personal tanks, I stock a little more heavily and do weekly 25-30% 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" of small fish per 2 gallons of water) and do 25% water changes every 2 weeks. The important thing to remember is that your water changes will have to keep up with the fish and food load in the tank. The more fish and feeding, the more water you're going to have 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 column. 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, no less than 25% per change until the algae problem is under control. You can go as high as 50% daily for a few days if absolutely necessary. I would also not add trace element supplements until this initial algae problem was 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, (i.e. rampant 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 rampant 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 on some of your "weeds" to someone else who needs to get started!

Question: Re: the green water, at least 4 or 5 of the APD regulars have offered up the opinion that green water flourishes in a nitrogen limited environment. I'm 2 weeks into being "certain" that nitrates are in the 5-10 mg./L range day-in/day-out and yet the problem persists. I've never had green water before, but I'm not so sure it's as simple as N-limited. I'm almost tempted not to change a thing and see if solving the N-limited problem will solve the green water. Others seem to be certain it will work!

You hit the nail on the head with dead plant material as part of the problem. While I was in Australia I had a die-off of lower leaves (esp. Hygrophila polysperma and Rotala macrandra) which got no help for a couple of weeks. I'm going after any die-off immediately now. I still have a bit of green filamentous algae (esp. older leaves of Echinodorus tenellus), so I think I'll cut out (or way back) on the Tropica Mastergrow until things get under control. If you were me, would you cut off the R. Macrandra and replant the stems? New growth is good, but 2-3 inches of the lower stems are bare.

Answer:
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, where others may not.

In my experience, green water is usually a sign of 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 over feeding or too heavy a fish load. 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 do 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 build-up. I prefer to watch my plants. Regardless of the test readings, 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 3 months old and completely stable) 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.

To cure a green water problem, I suggest the following approach:

Do several large water changes, both to remove nutrients and to reduce the number of algae cells.
At the same time, gravel vac any unplanted areas of the substrate thoroughly.
Then really darken the tank by turning out the lights, and wrapping the tank in towels to avoid ambient room light.
Do not feed the fish during this period, but you may take a peek now and then to make sure the fish are doing OK. Depending on the fish load, it may be necessary to install an air stone to increase water movement, as the plants will not be producing oxygen with the lights out.

In about 5 days, unwrap the tank. You should find that the water is crystal clear. As long as the underlying nutrient problem that caused the bloom was resolved first, the green water should not return.

As far as the Rotala macrandra is concerned, I routinely top mine and replant it. Left to its own devices, it would completely blanket the water surface! Snip the healthy tops off, just above the bare stems. Pull up and discard the bottoms, root and all. Replant the healthy stems no more than 2-3 at a time. The Rotala will develop a new root system extremely quickly under favorable conditions, and will start growing again immediately. Incidentally, If you want to increase the amount of Rotala macrandra you have quickly, allow the stems to grow tall enough that they lie across the surface of the water. You will find that they branch much more frequently if allowed to lie across the surface, and you'll have more than you know what to do with in short order!