Aquarium with Green Algae
Of all the irritating and unpleasant things that can happen to an aquarist, nothing is more likely to ruin his disposition and destroy his faith in the essentially benign purposes of nature than green water, particularly when it occurs, as it usually does, in a tank he is especially proud of or for some reason wants to watch closely.
The writer recalls vividly his own initial experience with this condition. He observed one morning that the water in his prize aquarium had lost its usual transparency. The next day it had a slightly green tinge. By the end of the week the contents of the tank had completely disappeared in a fog of pea soup, which the strongest light would not pierce. Hoping the condition was temporary and would clear itself up, he postponed doing anything about it, as the tank was a large one and cleaning it out would be no small job.
Finally deciding that further waiting was hopeless, he drew off all the water he could without removing about a hundred and fifty fish and replaced it with clear water. The improvement that resulted lasted only a few hours, and three days later the condition was worse than ever.
On the advice of more experienced friends the light was then cut down. The only result, after forty-eight hours, was to bring the fish to the surface gasping for air. Salt was added, likewise on the advice of friends. Effect-none. Other suggested remedies were tried without any improvement whatever, and finally the tank had to be cleaned out completely, washed, replanted and gotten off to a new start.
Following this experience an investigation was made which disclosed the following interesting facts: Water everywhere in indoor aquariums as well as outdoor ponds, etc., is constantly receiving air borne spores of algae, yeasts, molds and other bacteria. When the water contains appreciable percentages of dissolved or suspended organic matter, the spores develop into bacteria, which break down this matter into its component salts. These salts are the food of plants, and when there is sufficient actively growing plant life in the aquarium the salts are absorbed by the plants practically as fast as they are formed. Under these conditions an aquarium is “balanced" and the water remains sweet and clear indefinitely.
When, however, the salts referred to are formed faster than the plants can absorb them, the algae spores (which in effect are microscopic plant seeds) find a foothold and tiny microscopic plants which swim about in the water develop in prodigious numbers. These algae take up the excess salts and keep the water sweet, but unfortunately they also create an unsightly appearance. Moreover they compete with the higher plants in the aquarium, robbing them of both food and light. In time the higher plants will succumb, leaving the algae in full possession.
It will be seen therefore that the development of green water arises in the first place from an unbalanced condition in the aquarium. The decay and dissolution of an undue quantity of uneaten food, dead snails, fish, plant leaves, excrement, etc., leads to a high bacterial content (indicated by cloudy or ill smelling water) which produces more food than can be consumed by the plant life present in the tank. The algae step in and the tank becomes green.
Cutting down the light kills the algae, removing the effect without touching the cause. This is true of any other remedy which merely kills the algae. The sudden death and rapid decomposition of a quantity of algae may foul the tank and kill the fish. The only logical, safe and permanent remedy for green water is to reduce the amount of decomposing organic matter in the tank or increase the number of plants. This means:
- Find out whether the excess is caused by too many fish.
- If not, watch your feeding and siphon off the bottom dirt more frequently.