There are multiple ways to clean algae, diatoms, and other such growth off of filter components and ornaments. One of the simplest ways I have found is to remove the components from the tank and immerse them in a mix of chlorine bleach and water. Just regular, household chlorine bleach will work. I wouldn’t recommend bleach that contains perfumes or other such additives. Just plain, regular chlorine bleach.
I use a 10:1 mix – water to chlorine bleach. That is 10 parts water to one part chlorine. Place the component(s) in the bucket with the bleach and water mix then let sit for at least 24 hours. I use a one gallon bucket (pictured above), but a larger capacity may be necessary depending on the size of the components you are working with. Also make sure your bucket can safely hold chlorine bleach (i.e., that the material the bucket is constructed of can hold chlorine bleach).
After the algae, or whatever you’re trying to remove, has died, remove the components from the bucket and rinse them well. If the algae covering the item(s) is dense or heavy, there may be residual dead algae still clinging to the component(s). It will be a slimy, white to opaque colored sludge. This comes off very easily with a little light rinsing or scrubbing. Once rinsed, fill another one gallon bucket with fresh water and add three times the normal amount of water conditioner (chlorine/chloramine remover). Place the items in this clean water bucket and let them sit for another 24 hours. After that 24 hours, it’s not a bad idea to repeat the clean water soaking. Empty the fresh water bucket, refill, add water conditioner, and let the component(s) sit for another 24 hours. After that, simply rinse thoroughly under water, let air dray, and the items should be ready to reuse.
Usually, this is sufficient to completely wipe out anything organic on the component(s). I have used this on everything from PVC pieces to rocks to entire water pumps. It has been highly effective for me, but use this method at your own risk. There is no guarantee that this process won’t break, weaken, or otherwise disable the component(s) you treat. Nonetheless, I have yet to witness any degradation in the component(s) that I have exposed to this method.
WARNING NOTE: Always wear eye protection when working with chorine bleach. Rubber gloves are also advised. Be sure not to splash/spill the chlorine bleach or the chorine/water mixture on clothing or other items. If you have pets or small children, do not leave the bucket containing the bleach mixture within reach of them. Just like with any household chemical, use caution and common sense, and read the warnings when working with chorine bleach or around it. Also, do NOT pour chlorine bleach into any fish tank containing livestock (e.g., fish, crustaceans, plants, or anything living).