Aquarium using the best aquarium safe silicone to seal the edges

7 Best Aquarium Safe Silicone Options

Even the smallest of leaks in your aquarium can incite panic because it puts your plants and fish at serious risk. Low water levels due to leaks can cause spikes in hazardous compounds like ammonia and can damage your filter and heater. Finding the best aquarium-safe silicone option for your tank can help alleviate this stress. Our favorite aquarium-safe silicone option is Momentive RTV108-300ML Silicone.

Luckily, silicone is a quick-drying compound that’s easy to apply and will reestablish your tank’s seal. Some options also dry clear, so it’s an excellent adhesive for securing decorations in your aquarium. However, you’ll need to make sure you choose a silicone sealant that is safe for your tank and won’t harm or kill your fish.

Our reviews and comprehensive buyer’s guide below will help you decide on the best aquarium-safe silicone to seal or decorate your tank.

Best Aquarium-Safe Silicone Recommendations:

What is the Best Aquarium-Safe Silicone for My Fish Tank?

Our top pick for its strength, reliability, and safety is Momentive RTV108-300ML Silicone. It’s exceptionally durable once dried, comes in large quantities, and is made with translucent paste that makes it easy to fill cracks or large gaps in your glass.

7 Best Aquarium-Safe Silicone Options

1. Momentive RTV108-300ML Silicone

This silicone from Momentive is very powerful and will re-seal just about any gap in your tank without a problem. It will provide a fully waterproof seal that will likely last for years.

It’s made partially with paste to make it easy to fill in large gaps or build new tanks. The paste makes it translucent, so it’s not the best option for attaching decor.

It has a high viscosity and won’t drip, even if you place it on a vertical glass seam.

Most importantly, it’s USDA certified and completely safe for your fish and plants.


  • It comes in a large tube for ongoing repairs
  • The paste mixture makes it suitable for filling large gaps


  • It’s USDA certified and safe for fish and plants
  • It won’t drip when applied to vertical surfaces
  • It creates a very powerful, permanent seal


  • It’s relatively expensive
  • It doesn’t dry entirely clear

2. GE 1200 Series Construction Silicone Sealant

This silicone forms a strong and durable bond. It will hold its seal for quite some time. However, professional tank builders maintain that the seal isn’t as strong as our top pick.

It dries clear, so it won’t be too visible on glass seams. It’s an excellent option for attached decor because you won’t see globs of adhesive on each decoration in your tank.

It’s very affordable and comes in large quantities, so it’s great for those on a budget.

It’s safe for use in your tank and won’t be harmful to fish or plants.


  • It dries entirely clear
  • It forms a robust and durable seal


  • It is very affordable
  • It comes in large quantities
  • It’s great for attaching decor to your tank
  • It’s safe for fish and plants


  • It may drip during drying on vertical surfaces
  • It doesn’t form a seal as strong as our top pick

3. ASI Aquarium Sealant – Black Silicone

This silicone is black, so it’s not ideal for sealing vertical glass seams. However, it forms a strong bond and can be used for seams that will sit beneath your substrate. It’s best suited for attaching decorations where you don’t want algae to be visible.

This silicone comes in a large tube that should last you quite a long time. It’s very affordable and should fit into most aquarist’s budgets.

It won’t drip during sealing, and once it’s cured, it’s entirely safe for plants and fish.


  • It has a black color that fits in with dark aquarium setups
  • The thick formula won’t drip while it’s curing


  • The dark color hides algae well
  • It provides a very strong bond or seal in your tank
  • It comes in large quantities
  • It’s safe for plants and fish


  • The black color isn’t ideal for vertical glass seams
  • It will show up clearly in lighter-colored tanks

4. Loctite 908570 Clear Silicone

This silicone from Loctite dries completely clear, so it won’t be visible in your tank once it has cured. It’s great for visible portions of your tank where you don’t want to see globs of silicone.

It’s incredibly affordable, partially because it comes in a very small tube. The size doesn’t make it ideal for large scale sealing or tank building. However, the little applicator tip allows for precision, so it’s great to keep on hand to treat leaks and for decorating.

The silicone is safe for fish and plants once it cures and won’t cause any harm to your tank.


  • It includes a small applicator tip for precision
  • It dries entirely clear and won’t be visible in your tank


  • It’s suitable for small seals and attaching decorations
  • It’s very affordable
  • It is safe for fish and plants once cured


  • It only comes in small quantities
  • It isn’t ideal for building tanks or large seals

5. Aqueon Fish Tank Silicone Sealant

This silicone from Aqueon dries entirely clear and won’t be an eyesore in your tank once it cures. You can use it for building aquariums, sealing horizontal and vertical glass seams, and attaching decorations throughout your tank.

It’s designed specifically for aquarium use, and it’s completely safe for fish and plants once it’s dry.

It comes in a large tube and is relatively affordable. It creates a relatively strong bond that should maintain a waterproof seal for quite some time, although it may not last as long as other brands.


  • It dries entirely clear
  • The thick consistency won’t drip on vertical surfaces during curing


  • It’s strong enough for building and sealing tanks
  • It won’t be visible once it has cured
  • It comes in large quantities
  • It’s very affordable


  • The bond isn’t as strong as with some other brands
  • The large applicator makes detail work challenging

6. MarineLand Silicone Squeeze Tube

This silicone is made specifically for aquariums, and it’s guaranteed to be safe for plants and fish once it has dried.

It creates a strong enough bond to seal minor leaks, so it’s an excellent product to have on hand in case of emergencies. It dries clear and can be used for attaching or repairing decorations as well.

It comes in a small tube and is relatively expensive, especially given the small amount of silicone you get. As such, it’s not ideal for more extensive repairs. However, the little applicator makes precision work straightforward.


  • It’s made specifically for aquariums
  • It dries clear and won’t detract from your tank’s aesthetic


  • The small applicator makes detailed sealing or repairing effortless
  • It bonds strongly and will maintain a waterproof seal
  • It’s safe for plants and fish


  • It’s relatively expensive
  • It only comes in small quantities
  • It’s not ideal for large scale sealing or repairs

7. Dap 00688 All-Purpose Adhesive Sealant

This sealant is 100% silicone, so it’s entirely safe for plants and fish once it’s cured. It forms a tight, waterproof seal that is likely to last for quite some time.

It dries clear, which makes it an excellent option for repairing leaks on visible portions of your glass. You can also use it to attach or fix broken decorations, as it won’t detract from the look of your tank.

It is reasonably expensive, especially because you only get a small amount in each tube. However, the thin applicator makes applying small amounts straightforward, so it’s great for detail work.


  • It includes a small applicator designed for detail work in your tank
  • The clear-drying formula won’t detract from your aquarium’s aesthetic


  • It’s completely safe for fish and plants
  • It’s suitable for minor seals and decorating
  • It creates a tight, waterproof seal


  • It is relatively expensive
  • It only comes in small quantities
  • It isn’t practical for more extensive repairs or tank building

What is Aquarium-Safe Silicone? How Does it Work?

Silicone is a rubber-like polymer that creates a fully waterproof seal once it’s dried. It isn’t affected by submersion in freshwater or saltwater, and it doesn’t contain harmful chemicals once sealed.

Aquarium silicone typically comes in a tube with an applicator tip that spreads the compound over the area you’re looking to seal. Once dried, the seal is incredibly strong and waterproof.

What is the Difference Between Regular and Aquarium-Safe Silicone?

Regular silicone is used often in construction and for other waterproofing applications. It is sometimes mixed with other compounds that can be dangerous to your fish. These include additives to make it easier to apply or dry faster, or potentially harmful fungicides. While silicone is entirely safe for plants and fish, the added constituents may introduce dangerous chemicals into your water.

Aquarium-safe silicone uses only compounds that won’t break down in your water. Silicone designed for use in aquariums is 100% safe for fish, plants, bacteria, and other animals you may keep in your tank. It’s also designed to be strong enough to resist the pressure placed on it by many gallons of water found in aquariums.

Why Use Aquarium-Safe Silicone?

If you’re looking to seal a leak or seam or adhere anything in your tank, you absolutely need to use a silicone that is aquarium-safe. Some silicone products have additives that can make your tank water toxic, potentially killing your plants or fish.

Aquarium-safe silicone is typically safe and approved for direct contact with human food, so you can rest assured that it won’t be hazardous in the slightest to your tank inhabitants.

How to Use Aquarium-Safe Silicone?

You’ll apply aquarium-safe silicone differently depending on what you’re trying to accomplish.

1. For Tank Building and Repairing Leaks

To establish a new seal between glass seams or to repair a leak in your existing aquarium, you’re better off purchasing a larger tube of silicone. The bigger tubes are usually designed to be used with a caulk gun, so pick up one of those as well if you don’t already have one.

Make sure the application site is entirely dry, or you won’t get a waterproof seal. Position the applicator over the area you’re looking to seal, and squeeze the caulk gun trigger.

As the silicone comes out, slide the applicator along the length of the seam you’re sealing, doing your best to maintain an even bead of silicone. Once applied, you can run your finger or a silicone knife along the seam to smooth out the sealant.

Make sure you follow the directions for your silicone and let it completely dry before adding water to your tank.

2. For Attaching or Repairing Decorations

Smaller jobs, like attaching or repairing decorations in your tank, are best done with smaller squeeze tubes that have thinner applicators.

Again, make sure the application area is clean and entirely dry before you begin. Place a small amount of silicone on your decoration by squeezing the tube gently. Hold the piece against the surface you want to attach it to for several minutes.

Make sure you let the silicone cure entirely before adding any water to your tank.

Aquariums in pet store using the best aquarium safe silicone

How to Remove Aquarium-Safe Silicone?

If you’re looking to remove old aquarium-safe silicone before re-applying, or you want to remove silicone from where a decoration was previously attached to the glass, a razor blade is the best tool.

For small sections of silicone, you can simply scrape the razor blade along the pane of glass at an angle of about 30 degrees. This will remove the majority of the silicone remnants and will be sufficient for small pieces.

To remove silicone along entire glass seams, using a heat gun to soften it first is the best practice. Once the silicone is softened, you can use a razor blade to scrape it off without too much effort.

Aquarium-Safe Silicone FAQs

What Type of Silicone is Safe for Aquariums?

The best option to ensure the silicone you’re using is safe for aquariums is usually 100% silicone. Once pure silicone cures, it will never leach harmful chemicals into your tank water, so your fish and plants won’t be endangered.

However, some additives, like colors and thickeners, can also be safe for aquarium use. If you’re looking for a thick silicone that won’t drip or a black silicone to hide algae growth, make sure you buy a silicone product that is specifically labeled as being safe for aquariums.

Most silicone sealants have this distinction on the packaging, but food-safe or USDA-approved silicone products are also safe for your tank inhabitants.

Can I Use Any Kind of Silicone to Seal a Fish Tank?

No, not all types of silicone are safe or effective for sealing fish tanks.

Above all else, you need to make sure the silicone won’t leach dangerous chemicals into your tank water, as they can potentially kill your fish and plants. Always use a silicone labeled as safe for aquariums or food-safe.

Additionally, some silicone products are mixed with other constituents that don’t create as strong of a bond as pure silicone. Weaker bonds may not last as long or may lead to leaks once your tank water puts pressure on the seal. Again, using silicone that’s labeled as suitable for aquariums is an excellent way to ensure the seal you’ll create will be strong enough.

Where Do You Buy Aquarium-Safe Silicone?

You can purchase aquarium-safe silicone from a variety of online retailers, including Amazon. Most pet supply stores have silicone explicitly designed for fish tanks as well.

You can head to your local home improvement store to purchase it, but they will likely also have construction silicone as well that isn’t always safe for aquariums. If you do purchase from a store like Home Depot or Lowes, make sure you choose a product that is 100% silicone or labeled as safe for use in an aquarium.

What is the Best Aquarium-Safe Silicone for My Tank?

The best aquarium-safe silicone for your fish tank will be 100% silicone or specifically designed to be safe for use with fish and plants. It will come in a tube and have an applicator that makes application easy based on your intended use, either large scale sealing or detailed decoration placement. A good aquarium-safe silicone is important in any aquarist’s kit, as essential as a good canister filter or aquarium heater.

Our top pick for its strength, safety, and reliability is the Momentive RTV108-300ML Silicone. It’s the choice most often used by tank-building professionals, so you can be sure it will create a permanent, safe bond whether you’re assembling a tank, repairing a leak, or affixing a tank decoration.

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