Planted Tanks With Fish: Simple Steps to Success

by John Tullock

One of the most commonly asked questions I get regarding planted tanks goes something like: How do I keep it as simple as possible? While there really isn’t a short answer for that, here are some points to bear in mind when thinking about a planted aquarium with fish.

  1. Municipal tap water is satisfactory for the majority of situations. Be sure to use AquaLife Complete as directed to eliminate chlorine and other possible additives.
  2. Choose lighting that is intended for growing aquarium plants, and is of the correct intensity for your tank. As a rule, 50 PAR at the substrate is bright, while the minimum is about 20 PAR. Too much light can be as much of a problem as too little. Choose plants for low light, if going for a minimal system.
  3. Plants will grow well over a range of water conditions. However, without adequate carbon dioxide, light, and fertilizer, the plants will grow poorly and algae will invade.
  4. The best way to add carbon dioxide is with a pressurized system, such as Up-Aqua’s. The next best is an electrolytic system such as Sicce Life. The least effective is a liquid additive.
  5. Use a drop checker for routine monitoring of carbon dioxide.
  6. You MUST learn to use pH and KH test kits. KH MUST be above 3 dKH (53 mg/L) for carbon dioxide injection to be effective. Sorry, but this is due to the laws of chemistry.
  7. All plants should be added to the aquarium at once, or within a week to ten days’ time, and should be well-established and growing BEFORE fish are added. Not only does this insure good plant growth, it permits adjustments to water conditions without worrying about the impact on the fish. ALL OF THE FOCUS DURING THE FIRST MONTH MUST BE ON THE PLANTS.
  8. Planting technique matters. Do not leave plants in pots. Remove rock wool. Spread roots out.
  9. Algae grows because the plants are not doing well, or because certain nutrients are in great excess. Until plants are growing well, algae will ALWAYS return. Algae eaters alone won’t fix it.
  10. If the difference between pH measured one hour before the lights are turned on in the morning and one hour before they are turned off in the afternoon is greater than 0.1 pH unit, the plants are pulling out all available carbon dioxide. If alkalinity drops over the course of several days, carbon dioxide is severely depleted. Increase the CO2, or algae will begin to grow.
  11. A safe and effective range of carbon dioxide in a tank with fish is 20 to 30 ppm.
  12. Plants will need fertilization from the day after they are put into the aquarium. However, when fish go into the tank, the amount of fertilizer needed drops. You must either switch to a fertilizer made for use with lots of fish, or reduce the amount added. This is a matter of trial and error and observing how plants respond. If done properly, there should be no algae bloom when fish are added.
  13. As fish are added, all the usual cautions regarding ammonia and nitrite apply. However, a tank full of rapidly growing plants will use up all the ammonia from fish rapidly, if other conditions are correct. There is no need to “cycle” the tank if plants are grown for a month or more and fish are gradually introduced without overstocking.

You can download or print a copy of these guidelines here.

Pictured below is one of my experimental planted tanks, without fish. The first photo was taken on Thanksgiving Day, and the second one was taken this morning, December 9. Light intensity is 50 PAR at the substrate level, and the tank receives fertilizer every morning. I change 50% of the water weekly.

The aquarium in November.


The aquarium in December.

Growth of the Sagittaria has been the most rapid. Darkening of the brown coloration in the leaves of Cryptocoryne becketti is evident. Elapsed time between the photos is approximately two weeks. This is an example of plants being “well-established and growing.” There was no attempt at design with this aquarium Its purpose was to evaluate a system for optimal plant growth. This “farm tank” will continue to serve as a source of plants for more aquariums that we will exhibit on this web site.