Tang Fish and Algae Advice

Do tang fish eat algae in the aquarium?

Q. I hope you can give me some advice regarding tangs in my saltwater fish aquarium. I’m planning on buying one in the next few weeks, and from what I’ve seen there is quite a selection available. I’m having a small problem with hair algae, and read that certain tangs can help reduce this algae problem.

I have been interested in the powder blue tang, but have been told they are not very good eaters in captivity, they would not last more than a few months, and because they are costly, I should consider looking at a hardier type, like a yellow tang or a blue tang. I really like the sohal tang, but they are very costly, as are purple tangs. Any advice on the type of tang that would help my hair algae problem?

Also, could this hair algae be caused from excess nitrates or insufficient lighting? The last time I had the nitrates checked they were at 20 to 30 parts per million. I’ve been having difficulty reducing the nitrates lately.

My saltwater aquarium is 50 gallons and I have about 30 pounds of Marshall Island live rock in it. My fish consist of a flagfin angelfish, a maroon clown, a small green damsel, a royal gramma and a yellow watchman goby.

I do about a 10- to 15-gallon water change each month, and only add iodine and a strontium solution every week. I have only a small portion of crushed coral (size 10) on the aquarium bottom, and have been told that I would be better off leaving the bottom bare to reduce nitrates. Is this true? I would rather have some type of bottom layer because it looks so much better. Thanks for your time on these issues.

A. Let’s address your nitrate and marine algae problems first, and then turn our attention to the tangs. Although the nitrate level could be lower, it’s not unusually high. You mentioned that you like having substrate on the aquarium bottom because it looks so much better. Well, so do I!

If I were you I would mix some live sand in with your crushed coral so that the bottom is covered with approximately 2 inches of substrate. Also add some sifting gobies, like the orange-spotted sleeper goby (Valenciennea puellaris), to help keep the sand surface stirred (note: these gobies are great jumpers, so a top of some sort must be used to keep them in the aquarium). The organisms that live in the live sand, through the process of denitrification, can help bring your nitrate levels down.

If you add a tang to the aquarium you will have a pretty heavy fish load, which also equates to increased nutrient levels. I would invest in a good protein skimmer (you may have one, but you didn’t mention it) and stop adding iodine (unless you also have corals in the aquarium). You should add kalkwasser to your aquarium to boost calcium levels and encourage coralline algae growth, which will inhibit the growth of microalgae. I would make partial water changes every month (about 15 to 20 percent of water volume) using deionized water, and also use deionized water when topping off the aquarium as water evaporates.

Controlling nitrates, phosphates and dissolved organics can help make our fight against the green plague easier. There is no doubt that when there is a surplus of algal nutrients this botanical pest grows out of control, but I believe herbivores are essential to keeping an algae crop in check.

For example, studies conducted on coral reefs that occur in relatively nutrient-poor waters have demonstrated that if you exclude herbivores from an area, algae grows like mad! This indicates that the herbivores are very important in shaping the reef’s algae communities.

Our problem is to find fish and invertebrates that will eat the algae that has gone amuck in our aquariums. This brings us to the first part of your question — Which tangs are right for the job>>

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