algae on inside glass of fish tank

Question
Hi Nicole, I have 2 healthy goldfish in a 10 gallon tanl.  We change the water @ 25% intervals and the water is crystal clear.  We change the filter monthly.  But that awful algae build up on the inside of the tank glass.  We scrape it off monthly with a scraper from the pet store.  HOW CAN WE PREVENT THIS?  Do with have to remove the fish when we scrape the stuff off?  Our friend has 2 goldfish and states she has no algae problem.  How can this be?  Thank you so much, Nicole  P.S.  What is your middle name?

Answer
Hi Nicole,

There is probably a reason for the algae appearing in your tank and not your friends, but there are so many variables it is difficult to say. Her goldfish might be younger than yours - juvenile goldfish produce less waste. She may be feeding less, or feeding a different food. She may also just have a plecostomus, apple snail, or some other kind of "tank cleaner" which removes visible algae, but actually adds more waste to the tank, so is not really too worthwhile!

To beat algae, it is necessary to understand algae. It thrives in water with a high nutrient content, and it needs light to survive. Let's look at the light. Is this tank near a sunny window? That will do it. Do you leave your lights on too long? No more than 10 hours is recommended, unless you are keeping live plants - a whole other story.

Nutrients are a big deal. Even if the food looks like it is all going away, the fish excrement is still able to be used as food by the algae, so what you're going to have to do is feed low protein foods, and perhaps feed less, in order to make the water as low in nutrient content as possible. This is actually healthier for your goldfish!

First off, commercial foods should only make up about 50% of the diet. Goldfish do much better when fed vegetable material. Aquatic plants are the best, and you can read about what kinds to use here:
http://wetwebmedia.com/FWSubWebIndex/gldfshmalnut.htm

Vegetables such as zucchini, squash, cucumber and spinach also work:
http://www.kokosgoldfish.com/food.html
There, you can find a list of recommended foods for goldfish.

So if half of the time you're feeding these alternative foods, you're doing a lot to ensure your goldfish are healthy and your water is clean! Let's look at the other 50% of the diet. Make 25% be frozen foods such as vitamin enhanced brine shrimp, daphnia, or even meatier foods such as bloodworms and krill. As many varieties of frozen food as you can ought to be used, you can even occasionally offer mussels or clams from a can, if they will eat them.

The last 25% should be foods like goldfish crisps, flakes, and "veggie" flakes such as Spirulina flakes. Omega One makes an excellent veggie wafer and flake with Spirulina and kelp as the first ingredients. Goldfish also love wheat germ, you can either give them the kind that humans use (such as Kretschmer brand) or you can buy special wheat germ pellets for goldfish and koi, Hikari makes some.

If you step up the water changes to 50% a week, it will go a long way towards diluting the wastes which are ultimately playing a huge part in feeding the algae! Always use dechlorinator that removes chlorine and chloramine. I like Prime, by Seachem, in the 50 mL dropper bottle - just 2 drops of this stuff makes tap water safe for fish!

I also recommend you look into a product called Tetra Easy Balance. It has nitrate absorbing granules which will keep your water cleaner, it also has some buffers in it to keep the pH steady. Goldfish like a high pH, so make sure you don't use bottled water or water from a water softener - plain old unfiltered tap water, the harder the better, is what goldfish thrive in! Easy Balance is nothing like those awful "pH up" or "pH down" potions, it's very safe and mild.

I hope those suggestions help. Take care!
Nicole

P.S. My middle name is Alessandra. Kind of unusual, eh?