If you have high levels of phosphates in your fish tank, it will often result in an algae bloom. Yesterday, I mentioned adding Purigen (manufactured by Seachem) to your filter to absorb the excess phosphates.
But what do you do if your decorations have an algae growth you can't get rid of?
My first step is to clean the decoration with plain old baking soda. It won't harm the fish if any residue is left on, although it will alter your Ph so you'll want to monitor the Ph levels and add the necessary neutralizer or Ph adjustments.
I also have a toothbrush set aside to help knock off any algae growth and clean the decorations. Make sure it's a new toothbrush you use just for this purpose, as some toothpastes can leave a residue that could be harmful to your fish. I've seen stiffer brushes for sale and have used them, but often find the softer bristles of a toothbrush work best.
When the algae gets completed out of control, I use AlgaeFix. I never add this to the tank itself. That's very important. Even though the instructions say it's perfectly safe with fish, I've found it removes some of the nutrients from the water that the angels need to survive.
But I have an old water bucket set aside just for old fish water and cleanings, and I'll put the decoration into the bucket, fill it with water and add the AlgaeFix. Let it soak for a few hours or a few days, remove it and finish cleaning it up with that old toothbrush.
Make sure you rinse it off completely before adding it back into your tank. However, if any residue still exists on the decoration, unless you overused it, it should not have any adverse affect on your fish.
Tomorrow: how to keep phosphate levels at a healthy level.