To clean dirty fish tank glass. Well, we have the glass inside the aquarium and outside the aquarium.
Let's start with outside the aquarium. You want to use something that's not going to be toxic to the fish. If you're going to use Windex or some kind of spray cleaner please don't spray it directly on the tank. Even the slightest bit of molecules will find their way into the aquarium and could potentially kill some of the bacteria and harm the fish. So spray it on a towel or paper towel ten to 12 feet away from the aquarium, and then bring it to the aquarium and clean the glass with that.
I prefer using just regular warm water. For glass, newspaper works really well. It'll take that film, that salty film, off the aquarium. I've used newspapers for years to clean glass. It'll leave your fingers a little bit black, but it does really, really well at cleaning glass.
I wouldn't use it on acrylic because it'll scratch the acrylic. If you have acrylic or plexiglass you want to use a very soft terry cloth towel and a cleaner that's made to be used for acrylic. You don't want to use anything that's ammonia based as it'll burn and stain the acrylic.
So, to clean the dirty aquarium glass, the outside like fingerprints and stuff, just use regular water on a paper towel or a household towel. That usually cleans the outside of the aquarium just fine.
If you have hard water stains, like if you have hard water from keeping African cichlids and the water has dribbled down the side of the tank and it leaves that white crystal stuff, you could just dissolve the hard minerals in water. Just take some really wet towels and try to pat the aquarium, and keep doing that until you dissolve some of those minerals. There are also hard water stain removers. They sell them at fish stores just for this purpose. They're called Lime Away.
And on the inside of the aquarium if it's dirty you want to clean it. It's probably algae. You want to use a regular algae brush either handheld or on a stick and just get right in there. Or, use a magnet one on the outside and one on the inside, an aquarium magnet, and clean the algae that way.
And that's really the only dirt that you should find in the aquarium. You're not going to find detritus or waste settling on a viewing panel. It's going to be algae, so don't be afraid of it. If you wake up one day and your tank has a nice brown film on it don't get scared. We get calls to the fish store and our service company, oh my God, the water's brown, what is this, is the tank sick. No. It's just normal algae that's growing, diatom algae. So you just want to get in there and clean it out and not be afraid of it.