A determination of the bacterial and fungal flora of normal and iron containing fish aquaria

Roeder and Roeder (1963) observed a noticeable increase in the growth of the swordtail, Xiphophorus helleri. and the hybrid of the swordtail and platyfish, Xiphophorus maculatus, when small amounts of ferrous salt were added to aquaria. They also observed that the ferrous sulfate was quickly oxidized to ferric hydroxide and precipitated to the bottom of the tanks. They continued the experiment by studying four aquaria containing the hybrid fishes and four containing swordtails. To the first tank of each group they added no ferrous sulfate; to the second, 25 mg; to the third, 50 mg; and to the fourth, 100 mg of ferrous sulfate. Their results showed not only an increase in fish growth in each of the tanks containing iron, but also a growth increase that was proportional to the amount of iron added. I began experiments to determine whether the growth increase in the swordtails was related to a variation in the microflora of the fish tanks caused by the daily addition of iron. The experiments consisted of a comparison of predominant bacteria in fish tanks to which no iron had been added and tanks to which varying concentrations of iron had been added over a period of thirteen months