Aquarium Sealants: What You Need to Know

For any aquarium owner, keeping the tank watertight is crucial. Even the smallest leak can cause major damage and harm the fish. This is where aquarium sealants come in. Aquarium sealants are specially formulated adhesives to seal the seams and gaps in aquarium tanks. They provide a tight barrier that prevents water from escaping and contaminants from entering.

Choosing the right sealant is important, as is proper application and maintenance. With so many types and brands of aquarium sealants on the market, figuring out the ideal product for your needs can get confusing. This comprehensive guide covers everything you need to know about selecting, using, and caring for aquarium sealants.

What Are Aquarium Sealants?

Aquarium sealants are adhesives specifically designed for use in aquarium tanks. They seal the seams and gaps between glass panes or acrylic sheets to create a waterproof barrier. Aquarium sealants differ from regular household adhesives and caulking compounds in a few key ways:

  • They are non-toxic and fish-safe. Regular adhesives can leach harmful chemicals into the water, poisoning fish.
  • They are waterproof and retain bonding strength when submerged. Household adhesives become ineffective when wet.
  • They are flexible to absorb vibration and temperature changes. This prevents cracking or detaching from the surface over time.
  • They have anti-fungal properties to prevent mold or algae growth.
  • They are clear or tinted not to obstruct tank views.

Aquarium sealants provide a non-toxic waterproof seal capable of withstanding the unique conditions inside an aquarium. This keeps water in and contaminants out.

Types of Aquarium Sealants

Three main types of aquarium sealants are available: silicone, acrylic/solvent cement, and putty.

Silicone Sealant

Silicone is by far the most common aquarium sealant used today. It has many benefits that make it well-suited for aquariums:

  • 100% silicone formulas are non-toxic and fish safe once fully cured.
  • Silicone is extremely flexible and bonds well to glass or acrylic. This prevents cracking or detaching.
  • It has high adhesion strength to provide a permanent waterproof barrier.
  • Silicone is generally easy to apply, tool, and smooth out.
  • It is available in clear and various colored options.

Silicone sealants are best for sealing glass aquariums, as uncured silicone can damage acrylic. Neutral cure silicones are ideal, as acidic formulas can corrode metal fittings in a tank. Well-known brands like ASI and Aqueon manufacture high-quality silicone aquarium sealants.

Acrylic/Solvent Cement

Solvent cements are used primarily for acrylic or plexiglass aquariums. They provide an extremely strong chemical bond by partially dissolving and fusing acrylic surfaces together as the solvent evaporates. Key features include:

  • Bonds acrylic pieces into a seamless unit for maximum waterproofing.
  • Dries rigid and glass-clear for invisible seals.
  • Produces quick bonds and rapid cure times.
  • Not suitable for glass tanks – can damage silicone seals.

Popular solvent cement brands for aquariums include Weld-On and IPS. Proper ventilation is crucial when using these toxic cements.

Putty Sealants

Putty sealants traditionally consisted of plumber’s putty or linseed oil. They have been largely replaced by modern silicone and solvent cements, but still have niche uses:

  • Can seal minor leaks in existing tanks as a temporary fix.
  • Useful for sealing difficult areas like 3D tank decorations or irregular gaps.
  • Can be removed and reapplied more easily than permanent sealants.
  • It provides a good seal but lacks long-term durability and adhesion.

Putty sealants are best for small repairs and decor attachments. LeakSeal and Stik’N’Seal are two common aquarium putty brands.

Choosing the Right Aquarium Sealant

With the variety of sealants available, determining the best choice for your particular aquarium can be tricky. Here are tips for selecting the optimal product:

  • Silicone sealant is suitable for most standard glass aquariums. Opt for a 100% silicone formula labeled as aquarium-safe.
  • For acrylic or plexiglass tanks, use the proper acrylic solvent cement made for aquariums.
  • Match colored sealants to tinted tanks for visible seams. Clear silicone works for most applications.
  • For large aquariums, choose a high-performance sealant designed for maximum adhesion.
  • Quick-set formulas allow faster cure times to set up a new tank sooner.
  • Consider epoxy or urethane sealants for exposure to extreme conditions like outdoor ponds.
  • Check reviews and aquarium forum recommendations before purchasing a new sealant brand.

Top-rated and popular aquarium sealant brands include ASI, Loctite, Aqueon, GE Silicone I, and Marineland. Consult manufacturer instructions to ensure suitability for your particular tank.

How to Apply Aquarium Sealant

Applying aquarium sealant properly is just as important as choosing the right product. Follow these steps for best results:

Prep the Surface

  • Clean the surfaces thoroughly with isopropyl alcohol to remove residue, oils, and debris.
  • Buff acrylic lightly with fine sandpaper to roughen and improve adhesion.
  • Mask areas around joints with painter’s tape to reduce cleanup.

Apply the Sealant

  • Load sealant into a caulking gun if not using a squeeze tube. Cut the tip at a 45° angle for optimum flow.
  • Apply steady pressure while smoothing sealant into joints using a putty knife or smoothing tool.
  • Ensure complete coverage and a thickness of 1/8″ to 1⁄4″ for maximum seal integrity.
  • Wet your finger and tool with rubbing alcohol for smoothing silicone. Use the solvent itself for acrylic cement.
  • Stop and resmooth any uneven sections before moving on.

Finishing Touches

  • Strike the bead with a putty knife to create a concave shape and smooth finish.
  • Remove any excess sealant and masking tape after application.
  • Allow the full specified cure time before exposing sealant to water.

Proper smoothing and an even seal thickness are vital to create an impermeable seal. Take time with each joint for best waterproofing results.

Curing and Drying Aquarium Sealant

Patience is crucial when it comes to curing and drying of aquarium sealants. Filling a tank after applying a sealant may be tempting, but this can ruin all your hard work if the product isn’t fully set.

Here are general cure times to expect:

  • Silicone sealant: 48-72 hours for full cure and 7 days for maximum strength.
  • Acrylic cement: 24 hours is recommended for curing before water exposure.
  • Putty: Dries within 10-30 minutes but remains pliable.

Ensure any sealants have completely cured before filling your aquarium. Never rush this process. It allows sealants to set properly and prevents harming fish from leeching uncured chemicals.

Once cured, aquarium sealants are fully waterproof and retain maximum bonding strength when submerged. However, silicone sealant takes approximately 1-4 weeks to achieve its ultimate durability and adhesion capabilities.

Re-Sealing an Aquarium

Over time, aquarium sealants can deteriorate and need replacing to maintain a complete waterproof barrier. Here is an overview of the re-sealing process:

Drain and Remove Equipment

  • Drain tank completely and dispose of old sealant and water responsibly.
  • Remove and protect all equipment like filters, pumps, and heaters.

Cut Away Old Sealant

  • Use a sharp razor to remove all the existing sealant down to the glass or acrylic.
  • Take care not to scratch or damage surfaces.
  • Repeat until all traces of old sealant are removed. This provides a clean surface for new sealant to bond.

Clean Surfaces

  • Scrub inside seams and edges with a non-residue cleaner like isopropyl alcohol.
  • Use acetone or vinegar for final cleaning of acrylic tanks.
  • Ensure no old sealant or contaminants remain.

Re-seal the Aquarium

  • Follow sealant application directions above.
  • Allow for plenty of cure time before reintroducing water and fish.

Re-sealing requires time and care to remove old sealant and prep the tank properly. Patience in the re-application process helps ensure a successful repair.

Maintaining Aquarium Sealants

To get the most out of your aquarium sealants, proper maintenance is key:

  • Inspect seals regularly for cracks, gaps, or water drips requiring re-sealing.
  • Keep tank water chemistry balanced. High pH can degrade silicone over time.
  • Avoid harsh scrubbing or scraping that could damage sealant bonds.
  • Re-seal tanks every 3-5 years as preventative maintenance. Sealants weaken over time.
  • Watch for mineral deposits and algae accumulating along seals. Gently remove with a plastic scraper.
  • Keep tank equipment and decor from rubbing against or dislodging sealant. Allow 1-2″ of space around seals.
  • Use a siphon to remove gunk and debris from sealant during water changes.
  • Repair any damaged or detached sealant immediately before major leaks occur.

Aquarium sealants can last many years with proper application and routine care. But seal maintenance should be part of regular tank upkeep. Address any issues proactively to avoid the headache of major leaks or damage.

FAQs About Aquarium Sealants

Aquarium sealants play a vital role in maintaining the tank’s integrity, but many questions still arise for hobbyists. Here are answers to some of the most frequently asked questions:

What is the best aquarium sealant brand?

Top brands like ASI, Aqueon, and GE Silicone I are highly recommended for their quality and performance. Stick to sealants designed specifically for aquarium use.

How long does aquarium sealant take to cure?

Most silicone sealants take 24-72 hours to cure fully. Avoid filling the tank until the sealant has completely cured. Check manufacturer instructions.

Can I use regular silicone to seal an aquarium?

Household silicone may leach chemicals and should be avoided. Only use neutral-cure 100% silicone sealants marketed as aquarium-safe.

What’s the difference between silicone I and silicone II?

Silicone I offers better adhesion and is ideal for sealing aquariums. Silicone II has more flexibility but less sealing capability.

Can I reseal an aquarium with fish in it?

Not. The fumes are toxic and it’s impossible to clean and prepare the seals with fish present adequately.

How do I remove old aquarium sealant?

Use a sharp razor blade to cut away old sealant. Take care not to scratch the glass or acrylic. Remove all residue before re-sealing.

Does aquarium sealant expire?

Yes, though silicone will last about one year after opening. Inspect sealants for any drying or separation before use.

How do I fix a small aquarium leak?

Aquarium-safe putty can temporarily patch the leak for minor leaks until a full re-seal can be done.

Can I use acrylic cement on glass aquariums?

No, acrylic cement should only be used on acrylic tanks as it can damage glass and silicone seals.

How often should aquarium sealant be replaced?

Plan to re-seal the entire tank every 3-5 years as preventative maintenance to ensure water-tightness.

Aquarium Sealant Safety Tips

When working with aquarium sealants, following certain safety measures is important:

  • Work in a well-ventilated area, as fumes can be toxic.
  • Wear gloves and eye protection when handling sealants.
  • Thoroughly wash hands after application. Uncured sealant can be absorbed through skin.
  • Avoid contact with sealants if pregnant or chemical-sensitive.
  • Use razor blades carefully when scraping away old sealant.
  • Sealants and solvent cements are highly flammable. Allow all materials to cure and keep away from sparks or flames fully.
  • Dispose of used sealants responsibly as chemical waste. Never pour down drains.
  • Prevent children or pets from accessing uncured sealants.

While invaluable for aquariums, sealants do contain powerful chemicals. Taking appropriate safety measures helps mitigate risks.

Final Thoughts

The right aquarium sealant is essential for constructing a long-lasting, leakproof aquatic environment from silicone to solvent cement. Matching the sealant to the tank material, proper application, and routine maintenance are key to success. While initially daunting, re-sealing an aging aquarium helps extend its life. With some patience and the proper products, aquarium owners can master the art of DIY sealants. Just be sure to follow all safety precautions when working with these chemicals. Investing some time into the sealing process provides peace of mind knowing your aquarium will hold water and lock out contaminants.