Whether you’re building a new aquarium or repairing an old tank, you will need a trustworthy and reliable silicone to make sure that there are no leaks and that your tank holds together indefinitely. However, not every silicone product is made with aquariums in mind, so it’s important to know what makes something aquarium-safe while still giving the tightest seal.
Keep reading to find out everything you need to know about aquarium-safe silicone and some options that might be best for your tank build or repair!
Regular vs. aquarium-safe silicone
Silicone can be used to build or repair aquariums, as well as to secure rocks and driftwood or to make modifications to equipment. It is regularly used alongside types of cement and other glues, but silicone is usually most popular for sealing glass aquariums. While silicones can easily be found in your local hardware store, there are a few things to consider when purchasing a tube with aquarium-use in mind.
The problem is that many regular silicones include chemicals and other additives to combat issues that would arise outside of the aquarium environment, like mildew resistance and mold inhibitors; these unknown additives could eventually leak into the aquarium, causing more trouble than it’s worth. In order to find a completely aquarium-safe silicone, all you need to look for is a “100% silicone” label.
It should be noted that silicone does not work for acrylic fish tanks and does best when used on glass only.
How can you tell if silicone is safe for aquariums?
100% silicone is completely safe for aquariums as long as there are no sneaky additives; if it’s marked as pure silicone, it is safe. Some silicones go as far as to include “aquarium-safe” on their packaging, but this can often reflect on the price as well.
While some hobbyists standby specific aquarium brands to use in their systems, these products can sometimes be more expensive and come in smaller tubes even though they’re the same exact product as 100% non-toxic silicone. If you need that peace of mind, then there is no problem going with aquarium brand silicones. However, if you know what you’re looking for at your general hardware store, then you may save some money.
How does aquarium-safe silicone work?
Silicone is a silicon and oxygen water-resistant glue that can adhere to most surfaces, especially glass. This clear and flexible material is highly resistant to changes in pressure and other environmental conditions, including weather, sunlight, and temperature. Silicone is applied as a liquidy gel but gradually cures as a secure tacky putty.
For smaller tanks, it usually takes 24 hours for the silicone to cure. For larger tanks, it’s best to give as much time as possible for curing to make sure that there are no unfinished areas. The curing process must take place outside of the water and exposed to oxygen. It is best to perform a watertight test after the curing to make sure that no areas of the tank are lacking silicone.
For appearance purposes, it is also recommended to clean up any sloppy edges and remove excess silicone.
What silicone is safe for fish tanks?
There are a few aquarium silicone sealant products that seem to be especially tried and true for marine and freshwater hobbyists. In this list, we’ve included both generic and aquarium-specific silicone products so that you may decide which is better for your own setup and budget! We’ve also considered overall reliability, usage, price, and customer reviews.
Remember, it is recommended to have a layer of silicone that is as thick as the glass of the aquarium is, which means that it might be better to buy the larger tube or buy in bulk altogether!
GE Sealants & Adhesives GE012A All Purpose Silicone 1 Sealant, 10.1oz, Clear
- 100% WEATHERPROOF: This 100% silicone formula offers protection from water damage, providing a reliable seal in areas prone to weather and water exposure
- 7-YEAR MOLD-FREE PRODUCT PROTECTION: Protects against stain-causing mold and mildew growth
- EXCELLENT FLEXIBILITY & STRONG ADHESION: Provides a flexible, durable seal for both exterior and interior projects
The GE Sealants & Adhesives GE012A All Purpose Silicone 1 Sealant is probably the most recommended silicone for aquarium use, despite not being manufactured by a specialized brand. This silicone does best when cured for at least a week but can withstand extreme temperatures and will keep a strong seal for your fish tank; GE 1 comes in clear and white color options.
If you read the fine print on this sealant, you may find that it says “not safe for aquarium use”. Don’t be alarmed! Many hobbyists regularly use this silicone for their tanks without any problems as long as it is given time to fully cure. As long as the tube says 100% silicone without any additives, it should be safe for your fish, corals, plants, and invertebrates.
However, make sure to look out for GE Sealants & Adhesives GE5000 Advanced Silicone 2 Window & Door Sealant, which is not safe for aquariums. While some hobbyists say they have had no problems using GE 2 instead of GE 1, it’s generally agreed that GE 2 has been modified with mold-free properties and is designed for other purposes in mind that can be toxic.
Note: In recent years, this product has undergone a labeling change that guarantees 7-years mold-free. While it’s strongly believed that the actual ingredients across the rebranding stayed the same, if you want to be cautious, it’s recommended to look into other silicones.
What we like:
- 100% silicone favored by many hobbyists over the years
- Widely found in most hardware departments
- Strong, reliable seal given one-week curing time
What could be better:
- Long curing time
- Labeled as “not safe for aquarium use”
- Easily mixed up with GE 2
Aqueon Silicone Sealant
If you’re looking for an aquarium-specific brand for silicone, then Aqueon Silicone Sealant is guaranteed to be safe for your fish tank inhabitants. This clear silicone comes in four different packaging options: 1 ounce, 3 ounces, 10 ounces, and 10.3 oz/2 pack. Smaller options are better for attaching decorations or modifying filtration while the larger tubes will give the quantity needed to construct a tank or make larger changes.
This 100% aquarium-safe silicone is the same grade of strength as that used on new Aqueon tanks and typically cures within 48 hours, though we recommend giving as much time as possible to prevent any accidents.
The tubing and nozzle can be difficult to use if applying too much pressure at once, so make sure to only apply steady pressure. Some hobbyists have also found that the silicone has a tendency to dry up quickly if the cap is not completely fastened.
What we like:
- Trusted aquarium brand for guaranteed success with fish tank application
- Multiple sizes to choose from with varying nozzle sizes for different purposes
- Quick 48 hour curing time
What could be better:
- Tubing and nozzle sensitive to applied pressure
- Packaging design can cause the silicone to dry out
- Slightly more expensive than generic competitors
Dap 00688 All-Purpose Adhesive Sealant, 100% Silicone, 2.8-Ounce Tube
Dap 00688 All-Purpose Adhesive Sealant is a good choice of silicone if you need to fix emergency leaks or have smaller tanks or adjustments that need to be made.
This small tube of silicone is guaranteed to be aquarium-safe but isn’t made by an aquarium-specific brand and can usually be found at your local hardware store. Because it’s safe for everything from reef tanks to planted tanks and everything in between, hobbyists don’t need to worry about harmful additives affecting their tank.
However, this product comes in small packaging which probably isn’t ideal for larger tank builds in terms of price and quantity. This type of silicone also has a slightly longer curing time than Aqueon silicones, with an estimated time of about 72 hours; still, we recommend allowing as much time as possible before filling the tank with water.
What we like:
- Aquarium-safe 100% silicone
- Reasonable curing time of several days
- Smaller packaging for hard-to-reach areas/if large amounts of silicone aren’t needed
What could be better:
- Relatively expensive
ASI Clear Aquarium Silicone Sealant – 10.2 Fluid oz Cartridge
- Container size: 10.2 Oz. This high modulus component RTV Silicone Sealant forms strong cohesive bonds to glass without the need of primers
- The bonds are unaffected by continuous immersion in water and, when fully cured, is non-toxic to fish
- ASI Aquarium Silicone Sealant is a non-slump sealant and can be applied to vertical surfaces without flowing or sagging
If you want to assemble an industry-standard aquarium, it doesn’t get much more standard than ASI Clear Aquarium Silicone Sealant; ASI silicones are used on most aquariums you see in stores and comes in clear and black.
ASI silicones are specifically designed with freshwater and saltwater tanks in mind, offering durability, strength, and straightforward ingredients. However, this silicone can take a week or more to cure before being able to add water and fish to the aquarium, though this is worth it for such a strong bond.
It is crucial to follow instructions when using these silicones as it can be easy to apply too much at once or unevenly. It is strongly recommended to use gloves as the material can be sticky and also to work in a well-ventilated area as there is often a strong lingering odor. Because this product is so high quality, it is one of the most expensive options on this list.
What we like:
- The aquarium industry-standard for silicones
- Silicone designed specifically for fish tank setups
- Built to last with tight seals
What could be better:
- Not completely beginner-friendly
- Long curing time of a week or more?
- Difficult material to work with in terms of touch and smell
While you might not be building a tank, fixing a repair, or making modifications to equipment/decorations, aquarium silicone is very convenient to have on hand. If unopened, many silicones will last a few years, during which you hopefully won’t need to use them!
Otherwise, it’s important to consider where you will need to use the silicone, how long you have to wait for curing, color, and price; different silicones come in different sizes, making it easier or harder to reach some areas in the tank, sump, or filter.
As long as the silicone is labeled as 100% silicone without any additives or chemicals, then it should be aquarium-safe. If you have any doubts, there are also a number of aquarium-specific brands that have perfected silicones for aquariums!
If you have any questions about aquarium silicone, how to build a glass fish tank, or have had experience using any of the silicones on this list, don’t hesitate to leave a comment below!