Algae Scraper for Giant Tank

jossswonk · Apr 30, 2026

Hi guys! At the place where I work we have a massive 800 gallon hexagon tank in the lobby. Over the years it has had some serious algae issues. While its better since we've modified it a bit, it still gets some really tough algae on the glass that can't be removed with our magnet scrubber. The only way that we can remove it is by putting someone in the tank with a razorblade. Does anyone know of any contraption that we could either buy or make that would be able to help us? Preferably a magnet scrubber that has a blade attachment of some sort? We have already tried reducing the lighting and using a UV sterilizer. Any guidance that anyone could give us will be much appreciated.

BanjoFish · Apr 30, 2026

a fish?

Uberhoust · Apr 30, 2026

You might have to make something custom, like a magic erasure on a long pole. I imagine this is an acrylic tank, is so then you have to be a bit more careful with cleaning devices that use a sharp edge. You might be able to find something in a hardware store used to scrape flooring our paint off.

jaylach · Apr 30, 2026

On a tank that size I'd consider an ice scraper such as what you would to scrape off your car's windshield in winter.

As a natural help cut down on the hours per day the tank is lit with lights. Also cut down a bit on feeding. Fish don't need the high caloric intake as mammals and birds. It's been ages but I'll try to give correct numbers. A mammal or bird uses around 75% of their caloric intake to maintain body temperature. With fish the body temperature is controlled by the water temperature so they need much less caloric intake. Except for special situations fish do not need to be fed every day. I tend to feed 5 days a week but, for most fish, every other day is sufficient.

Algae is normally caused by too much light and food. Cut down on both and you will likely have much less algae.

jossswonk · Apr 30, 2026

We have cut down on both light and food. We feed Mon, Wed, and Fri, and the light is on for 5-6 hours a day since it's a public building. There's a bunch of natural light that's coming in from the windows next to the tank so I've asked my boss if we could get maintenance to install curtains to block the light during the brightest parts of the day. The tank gets a 25% water change every week, but when summer starts I think I'm going to start cleaning it twice a week to try to see if that helps. These are all very good ideas! At the moment we use a magnet scrubber, but it just doesn't get the tough algae. We might try a couple ideas out to see what works.

Magnum Man · Apr 30, 2026

is it glass , or acrylic???

jossswonk · Apr 30, 2026

It's acrylic

jaylach · May 1, 2026

jossswonk said:
It's acrylic

In that case try softer scrapers or sponge to avoid scratching.

GaryE · May 1, 2026

It just looks like scratching waiting to happen...

Mazain · May 4, 2026

From the looks of it the routine maintanance has passed on cleaning the glass. To minimise the cause you could either add a water treament for the tank water along with some easy growing plants.

Archerfish · May 4, 2026

Nice tank, @jossswonk! I suggest you contact a public aquarium to see what they use. Try contacting the Mississippi River Museum in Dubuque, Iowa. They might be able to provide some good advice.

jossswonk · Jun 2, 2026

If anyone was curious, I had the idea to test out a toilet brush on the top on the acrilic that wasn't visible and it was able to remove algae without scratching!

jaylach · Jun 2, 2026

jossswonk said:
If anyone was curious, I had the idea to test out a toilet brush on the top on the acrilic that wasn't visible and it was able to remove algae without scratching!

LOL! Hope it wasn't a used brush.

Good job.