How To Clean Fish Tank Decorations

When we became proud new fish owners, we let our kids pick out a decoration for our family aquarium. But one day, our youngest pointed out how our charming decor went from sparkling white to green.

Needless to say, we didn’t know anything about how to clean fish tank decorations. But now we do, and we’ll share the tips we learned. Keep reading so that you can skip the trial and error!

A Note Before Starting

It’s natural for beginner fish keepers to assume they can clean all of their fish tank decorations at once. However, aquarium ornaments contain beneficial bacteria that support the nitrogen cycle.

Since aquariums can fill with nitrite due to ammonia and waste in the water, the nitrogen cycle proactively breaks down these toxins before they can kill your fish using beneficial bacteria.

So, assess the number of tank decorations in your tank and clean them in small groups, letting a week or more pass between cleanings so that your tank has time to cycle. That way, your newly cleaned decorations will have time to build up a new layer of this nitrifying bacteria (which, thankfully, is invisible to the naked eye).

How To Clean Fish Tank Decorations

Step 1: Wash Your Hands

You’ll need to stick your hands and arm into the aquarium to remove your decorations. With that in mind, you’ll want to wash them to remove bacteria, oil, moisturizer, and any other residue they might be carrying.

Whereas soap benefits us large species as humans, it can have a detrimental—and even deadly—impact on fish. Ecologists have shown that soap and detergent negatively impact a fish’s food in the wild, as it removes the protective waxes that allow an insect’s cell membranes to function.

Needless to say, after washing your hands and arm well with soap, take the time to rinse them thoroughly. It’s an excellent opportunity to turn this into a hygiene lesson for your kids if they’re excited about helping clean the fish tank decorations. 

Step 2: Boil Water

Once you safely remove a portion of the decorations from your fish tank, set them aside and boil a pot of water. 

Although you shouldn’t need to purchase new materials once you learn how to clean fish tank decorations and do it for the first time, some fish keepers prefer to have an old, separate pot dedicated to this process.

Even though you can boil water in a microwave, we recommend doing so over the stove. 

It takes at least two minutes of water remaining at a rolling boil in a microwave to have a sanitation effect, although the exact time depends on your altitude. The higher it is, the longer you’ll need to boil water. 

Step 3: Soak Your Decorations

Remove the boiling pot of water from your stove and set it on a burner that you keep turned off. 

Then, gently place your tank decorations in the pot. The hot water will work to soften and kill algae, but since the water is no longer boiling, it shouldn’t damage the decorations in bubbling water.

Nevertheless, low-quality tank decorations may crack or melt during this process, so you might want to warn your kids if they’re partial to a particular decoration.

Consider any cracked or melted decorations a blessing; you wouldn’t want them in your fish’s aquarium in the long term. 

We recommend leaving your decorations in hot water for a minimum of 20 minutes.

Step 4: Target Hard-to-Reach Corners

When it’s time to remove your tank decorations from the pot, the water will still be hot, so use tongs to grab them. Set the decorations on an old towel, and pull out a toothbrush—ensure it’s a new, unused toothbrush.

If the tank decorations are too hot to handle, use rubber oven mitts or another towel to hold them while you scrub the toothbrush in areas of your decorations where you see algae.

The hot water should have removed some of the algae, but it’s common for it to remain in cracks. Moreover, the length of time since you placed your decorations in your aquarium will also impact how hard it’ll be to scrub off the algae.

How To Clean Fish Tank Decorations

Step 5: Use Bleach (Optional)

You don’t need to use bleach when learning how to clean fish tank decorations. But we do think it’s worth mentioning this step, particularly if you have a situation on your hands where you can’t get your decorations back to their original vibrant state.

Should you wish to use bleach to kill any potential remaining algae and give your decorations a facelift, mix 5% bleach with 95% cool to lukewarm water.

That equates to only four teaspoons of bleach for two gallons of water, which should be plenty to target one or two of the decorations you’re cleaning.

You should use bottled water for this step, as the chlorine in your tap water is deadly to fish. Alternatively, you can let tap water sit on your kitchen counter for 24 hours, allowing aeration to remove this chemical naturally.

Let your decorations sit in the bleach solution for five minutes. Then, make any final touches you see fit by scrubbing your decoration before moving to the final cleaning stage.

Step 6: Perform a Cold Water Soak

Run cold, non-chlorinated water over your decorations if you bleach them. If you didn’t use bleach, move straight to filling up a bucket with dechlorinated tap water. Make sure the water is warmer than lukewarm, but not hot.

However, if you didn’t plan ahead with dechlorinating your tap water, you can always run out to the store and purchase dechlorinating tablets to make the water safe and near-instantly useable. 

Afterward, let your decorations sit in this dechlorinated water for 20 minutes. 

The importance of using dechlorinated water for this final step and giving your decorations so much time is to prevent any porous areas from carrying chlorine or bleach into the tank. Both will kill your fish. 

Step 7: Replace the Decorations

Check to ensure your tank decorations are still in good shape. If they seem weak because of the cleaning process, it’s better to throw them away.

Then, rewash your hands and arm, and place the decorations back into your aquarium.

Should you wish to change up the location of your decorations or plants, do so gradually. Fish are highly sensitive to changes in their environment. 

Therefore, consider moving one or two decorations or plants at a time, allowing a few days in between. That way, your fish have time to adjust to the changes, and you’ll reduce the chances of them becoming stressed, which increases the likelihood of them suffering from diseases.

How Often Should I Clean Fish Tank Decorations?

The frequency of cleaning your fish tank decorations varies considerably depending on your circumstances. However, we’ve seen people advocate cleaning them once per month.

The reason is that how fast tank decorations become dirty can reflect the overall cleanliness of the tank. We place a huge emphasis on ensuring we have a high-quality filter, and we use a sponge to stay on top of algae growing on the sides of our glass tank.

Additionally, algae eaters are an effective way of cutting back on how fast your tank decorations become dirty. So, if you don’t already have some in your tank, you might want to consider adding a few—assuming, of course, that your other fish will get along with them.

That said, the more frequently you clean your fish tank decorations, the lower the chance you’ll encounter algae sticking so stubbornly to them that you need to use bleach.


Maintain a regular schedule for cleaning your fish tank decorations and keep your aquarium looking beautiful!

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