Everything You Need to Know About Aquarium Silicone

. in Maintenance

Everything You Need to Know About Aquarium Silicone

Aquarium Silicone needs to be safe for your fish.  Silicone is a rubber compound that, once cured, forms a waterproof tight seal.  Silicones are manufactured with different components, to dry the product quickly, coloring agents and preservatives.  The added ingredients mean not all silicones can be used on your fish tank.  High-quality food-safe sealant will not leach elements into your aquarium, but silicone manufactured for aquariums will last longer.  We review the four tried and tested aquarium silicones.

Silicone being rubber is flexible rather than rigid, keeping it from breaking under pressure as the water moves in your fish tank.  In your aquarium, it will last anywhere from 10 to 15 years; however, if stored, the aquarium silicone will dry crack and perish faster.

Check stored or secondhand fish tanks for damaged silicone:

  • Any area that is discolored
  • Run your fingernail along the edge to check for damaged
  • A large number of air pockets
  • Check for slow leaks

Find out how to clean a secondhand fish tank by reading our article How to Clean a Freshwater Fish Tank (A Step by Step Guide)

Silicone will bond together quickly, but it takes 24 – 48 hours before it cures completely to form a waterproof seal.  This curing time is dependent on environmental factors, sunlight, moisture, and heat.  Once cured, fill the aquarium with water and wait two weeks to ensure that there are no slow leaks. 

Aquarium Silicone Reviews

Things to remember:

  • Silicone does not bond to old silicone
  • Do not apply on a wet or dirty surface
  • Safe aquarium silicone is non-toxic after curing
  • Curing time is dependent on environmental factors and can take up to 7 days to completely cure in cold or dry climates
  • You can’t paint over silicone
  • Please read the list of ingredients on the bottle; if it has no additives it can be used as aquarium silicone

Best Aquarium Silicones

#1 – Aqueon Silicone Sealant



Aqueon Silicone is one of the best aquarium silicones on the market today.  One of the few with a handy 3oz tube convenient to have on hand for a quick patch or join decorations together. If you are adding plants to hardwood, use florist oasis glue and not silicone.  Silicone is toxic when wet, and it must not touch the water as it dries. 

If your fish tank has sprung a leak, the 10.3 oz pack is the way to go for resealing aquariums.  Silicone does not stick to old silicone; it may hold for a few weeks or slow the leak, but it will pull away, making the hole bigger.  Remove it with a blade and wipe down with rubbing alcohol to remove all residue.  Please wait a few minutes for the alcohol to dry before applying the sealant as it will breakdown and degrade the product.


q? encoding=UTF8&ASIN=B0002ASD2K&Format= SL250 &ID=AsinImage&MarketPlace=US&ServiceVersion=20070822&WS=1&tag=focuslifeguid 20&language=en USir?t=focuslifeguid 20&language=en US&l=li3&o=1&a=B0002ASD2K



Our Verdict

Aqueon Silicone Sealant is the best on the market.  Non-toxic but takes more time to cure.  In an emergency, it may not be the best to use.  Use black silicone on aquariums with caution, and only if you have the time to smooth the edges.  Long-lasting and withstands the pressure of the movement within the fish tank, it is worth the extra dry time.

Be careful before you add any element to your fish tank; if you are hardscaping read our article How to Choose the Best Aquarium Driftwood

#2 – SOMAFIX Aquarium Silicone Sealant


The Soafix aquarium silicone has a great price.  The best part is that it comes with two spare nozzles, which means you only have to buy a silicone tool to create a neat smooth edge.  It has a long-lasting bond and, once dry, has a non-toxic waterproof seal.  Once the smell dissipates, the silicone is cured, this product has a potent aroma, and it is easy to tell if it is dry.  The manufactures’ label will give you an indication. 

Still, the curing times differ depending on the weather elements, especially moisture and heat, that play a significant role in the drying time.  This sealant is hardwearing and safe to seal your fish tank with.  It is able to withstand extreme temperatures and is perfect for use on ponds too.



Our Verdict

The somafix sealant dries faster than the Aqueon Silicone.  This silicone is excellent if you can’t wait for the product to dry, or you have a pond.  However, the smell is overpowering, and if you can wait a few hours longer, it is better to use another product.  If you do use it, use this aquarium silicone outside.

Thinking of upgrading your pond to a Koi Pond read Everything You Need to Know About Building and Maintaining a Koi Pond

#3 – Loctite Clear Silicone Waterproof Sealant


The Loctite clear silicone is clean and comes in a small tube able to bonds several types of materials together, making it perfect as a glue for decorating or attaching items to the aquarium glass and building hardscapes décor.  Silicone degrades in the tube over time, and small containers have just enough product for these jobs where larger ones will lead to wasting much of the product. 

This sealant, however, has one problem, and that is the packaging comes apart with only a little pressure.  If you are planning to reuse it, you need to be careful when squeezing out the sealant.  The silicone will be stuck in the lid the next time you try to use it, but if you cut off the top piece of the lid, the product below may still be useable.



Our Verdict

It is a quick-drying seal, use with care as the packaging is likely to split open, and the rest of the product will dry in a few hours rendering it useless.

#4 – Momentive RTV100 Series


The Momentive RTV100 Series is comparable with the Aqueon Silicone Sealant as an aquarium silicone, and this sealant is ideal for large fish tanks.  The curing time is long but, once cured, can withstand high pressure and movement.  Some people are put off by the curing time, but the longer it takes for silicone to dry, the more chains have been formed, and thus it has a stronger bond.  Once dry, it is non-toxic. 

The Momentive silicone sealant is more expensive than other aquarium silicones but is the popular choice for many professional fish tank builders.  The sealant comes in both clear and black making it perfect if you want to create an edge, have a transparent border, or to repair equipment.



Our Verdict

A building grade sealant is perfect for large fish tanks and holds under high pressure.  Once cured, it forms a tight bond and a flexible seal. The extended drying time may be an issue for repairing the fish tank, but in hot wet climates, the curing time is reduced.

FAQ’s on Aquarium Silicone

How to Reseal an Aquarium?

Resealing a fish tank is easy; first, empty the fish tank of all water.

Removing silicon from glass: Scrape a blade between the glass and the silicone until the edges separate and clean the sides until all visible silicone is removed.  Use rubbing alcohol or acetone to remove the residue and leave to dry.

To reseal an aquarium:  add guide tape on either side of the edges.  Add three thick strips on the outside of the glass. 

To apply silicone sealant, use a silicone gun to draw beads between the guides place the joining glass on top.  Smooth the edges with a silicone tool before joining with the three external tape strips to hold it in place.

Cure as per the manufacturer’s directions. If you need more instructions, check out How to Build Your Own DIY Fish Tank – A Step by Step Guide

How Long Does It Take Silicone to Dry?

The curing time of silicone differs between brands and is dependent on the climate.  Most silicones take 24 to 48 hours to cure in warm weather and can take a bit longer before it is safe to use as aquarium silicone.  Once cured, silicone is waterproof forever; leaks form as the silicone shrinks and lifts from the edge of the glass, which takes anywhere from 10 to 15 years.

Once silicone comes into contact with air, links are created, and these links are bounded together.  The chemical reaction continues for days until the chains and links are numerous, and the seal is firm.  To know when silicone is dry, check out when the smell disappears; be careful not to touch it too early as you can damage the finish.

What Happens if Caulk Gets Wet Before It Cures?

Moisture speeds up the drying process, but you can’t use it in your fish tank.  It is harmful to fish and plants until it is dry.  If your aquarium is wet when you apply silicone, it can cause unsightly bubbles and ridges, which makes the finish untidy.

How to Glue Rocks Together for Landscaping?

To glue rocks together in hardscaping waterproof super glue works the best, but you can use a small tube or left-over aquarium silicone.  Either way, cover the adhesive with bits of tiny rocks, making the join invisible.

Aquascaping?  You need to know about rocks and how to test if they are safe to use in your fish tank.

Also read – How to Choose the Right Aquarium Rocks and Substrate for Saltwater and Freshwater Tanks

Can You Use Regular Silicone to Seal a Fish Tank?

The type of silicone that is aquarium safe are silicones that are 100% silicone and have no additives.  Read the ingredient label on the back of the product to make sure what the adhesive contains.  Fungicides and antimicrobials are excellent for showers but bad for aquariums.

What to Do if Your Fish Tank Has Sprung a Leak

All silicone, even the best ones, will perish over time.  If you have a fish tank that has been in storage for a while, aquarium silicone will degrade faster than when it is in use; if you buy a secondhand fish tank or pull one out of storage check if the silicone lifts or for slow leaks before you fill the aquarium with fish.

Wet silicone is toxic, use aquarium silicone in an emergency if the leak is high on the seal and if you can drain the water below this point without harming your fish.  This patch will only buy you time while you find your fish a new home to make proper repairs.  Duct tape can seal your tank if the leak is lower while you prepare a new home for your fish. 

While having prepared water is essential, you can empty the aquarium into any food-grade container that is large enough to accommodate your fish and is heat resistant.  Removing silicone when wet isn’t a problem, but you must clean and allow the glass to dry before you apply new aquarium silicone.  You can use silicone that contains no additives for aquariums.  Once opened, silicone doesn’t last long; only buy the quantity you need.

RODI water can keep for up to 2 years if stored in a food-grade airtight container, having some on hand will help in an emergency.  Read all about RODI Water in our article How to Use RODI Water to Create the Best Water for Your Aquarium

Sharing is caring!

Leave a Comment