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The Best Aquarium Safe Expanding Foam On The Market!

As aquascaping and aquarium customisation both become more and more people amongst the fish keeping community, we have noticed more and more people reaching out and asking for advice on aquarium safe expanding foam over the last few months.

With it essentially being a minefield when it comes to finding an aquarium safe expanding foam product on the market, we wanted to publish our own article going over the topic in the hope that we will be able to help as many of our readers as possible.

Now, keep in mind that although people may use one expanding foam product in their aquarium and not have any problems, this does not mean that this will be the same for you due to the differences in the animals and plants that you keep.

For example, the more sensitive fish species or some sensitive corals can have problems with even a slight chance to their water parameters where as other fish can be fine and not have any issues in the exact same water.

At the time of writing, we are not aware of any expanding foam product that has been specifically designed for use in aquariums but the majority of fish keepers who are involved in aquascaping or tank customization usually go with Great Stuff Pond & Stone Expanding Foam and don’t end up having problems.

As we mentioned though, although Great Stuff Pond & Stone Expanding Foam is a very popular choice for expanding foam within the fish keeping community, using it in your aquarium is an off-label use so there will always be some level of risk.

Is Expanding Foam Safe For Aquariums?

The majority of expanding foam products are not considered aquarium safe and most will end up causing problems with your water parameters and result in serious issues with your fish and live plants.

Thankfully though, there are some expanding foam products on the market that are commonly used in aquariums and cause minimal issues provided you leave the foam to fully cure prior to adding water to the tank.

If you are planning on aquascaping a tank from scratch then this does tend to be easy enough to work in to your overall plan as you will often build up an aquascape in stages offering plenty of time for your expanding foam to fully cure prior to adding water to your aquarium.

Great Stuff Pond & Stone Expanding Foam is by far the most popular option in this case but people also use the expanding foam for some other use cases in their aquarium too.

Just keep in mind that you should never be applying any expanding foam to an aquarium full of water due to the foam leaking various toxins while expanding.

Provided you only apply the expanding foam above the waterline, you can end up getting good results though and use the foam in a number of different situations without putting the occupants of your tank at risk.

The Best Aquarium Safe Expanding Foam!

We have to go with Great Stuff Pond & Stone Expanding Foam as the best expanding foam for aquariums and although it is not marked as aquarium safe, a huge number of fish keepers use it as their expanding foam of choice in their aquarium without issue.

Many popular aquascapers from social media also use it as their expanding foam of choice for the aquascapes they build in their tanks too showing just how well it can be implemented into a tank.

As we mentioned back at the start of the article though, using Great Stuff Pond & Stone Expanding Foam in your aquarium is an off-label use and there will always be some level of risk no matter how small.

Just because a large number of other fish keepers have successfully used the expanding foam in their aquariums without issue does not mean that the same can be said for you but the majority of the time, we would expect it to be fine for most of our readers.

One way that you are able to reduce the risk of using this expanding foam in your aquarium is to set it up, leave it to cure fully, fill the tank for water and leave it for a week or two.

Then test the water parameters with a water test kit to see if it identifies any issues with your water, keep in mind that some of the cheaper water test kits only test for very basic problems with your water.

Looking for obvious issues with your water too such as chemicals floating on the surface can also be an indication of any potential problems too.

Is Great Stuff Foam Toxic to Fish?

The Great Stuff expanding foam range have a number of different formulas that are all designed for different use cases.

The Great Stuff Pond & Stone Expanding Foam is the most popular option from their range to be used in aquariums and ponds with minimal issues being reported from a huge number of fish keepers who use the product.

Please note that other products from the Great Stuff foam range are definitely not suitable for use as an expanding foam product in your aquarium though so always be sure to use the Great Stuff Pond & Stone Expanding Foam when looking for an expanding foam product for your aquariums and fish tanks.

In all honesty, we would never recommend that you even try any other expanding foam products from other brands in your tanks at this stage as there have just been so many horror stories of aquariums being wiped out due to using unsuitable expanding foam.

We do hope that a brand will release an officially tested aquarium safe expanding foam soon but we are not holding much hope for it due to the market simply being too small.

This is why the majority of people just go with Great Stuff Pond & Stone Expanding Foam as there are no real other options available and we doubt that this is going to change any time soon.

Do You Have To Let Expanding Foam Fully Cure Before Adding Water To Your Tank?

You should always leave expanding foam to fully cure in your aquarium before you add water to the tank.

The curing process is what locks the foam down and produces the protective barrier on the surface of the foam to prevent any chemicals or potential toxins from leaving out into your water.

One very common problem that we see people make time and time again is that cured and dry is not the same state for expanding foam.

Some products can dry surprisingly quickly but may require weeks to fully cure so always check the label of the specific product that you are planning to use in your aquarium to get the recommended cure time for the foam.

Some people do like to be extra safe and wait and extra few days in addition to the recommended cure time too but this is not usually essential.

Please take note that letting an unsuitable expanding foam dry for its full cure time will not make it safe for use in aquariums and you will still have to use something that poses minimal risk to your fish.


That brings our article going over the best aquarium safe expanding foam on the market right now to an end. We hope that we have been able to help our readers better understand what they should be using in their aquariums and fish tanks if they do need some expanding foam for whatever reason in their tank. Unfortunately, there really is only one suitable product on the market right now with Great Stuff Pond & Stone Expanding Foam being the only formula that we feel comfortable recommending to our readers.