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American Sealants Inc

Aquarium Silicon 509 ASI

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$19.99
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Packed with care, every time

Livestock orders are double-bagged, insulated, and shipped with a heat or ice pack based on your destination's weather, so your fish and coral arrive healthy and ready for your tank.

Free shipping over $299
Live arrival guarantee
Trusted since 1991

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Email (305) 227-9414

ASI 509 Aquarium Silicone (sometimes written as “Aquarium Silicone 509 ASI”) is a professional-grade aquarium-safe RTV silicone sealant used for building and repairing fish tanks.

What it is

  • A 100% RTV (room-temperature vulcanizing) silicone
  • Designed specifically for aquariums, terrariums, and glass panel sealing
  • Cures into a flexible rubber-like waterproof bond

Key features

  • Aquarium safe (safe for freshwater & saltwater once fully cured)
  • Strong adhesion to glass without primer
  • High strength + flexibility (handles water pressure and tank movement)
  • Non-slump formula (won’t sag on vertical seams)
  • Clear or black options
  • Resistant to long-term water exposure and yellowing  

What it’s used for in aquariums

  • Sealing aquarium corners and seams
  • Rebuilding or resealing tanks
  • Installing or repairing baffles in sumps
  • Bonding glass panels in custom tanks
  • General reef tank repairs

Important notes (this matters)

  • Must be fully cured (usually 24–48+ hours, sometimes longer for thick beads) before adding water or livestock
  • Old silicone must be completely removed before resealing (new silicone doesn’t properly bond to old cured silicone)
  • Avoid contamination (oils, dust, wet glass)

Why reef builders use it

It’s basically considered a “pro builder” silicone—the same type used in manufacturing aquariums, not just DIY repair kits.

All livestock ships via FedEx Priority Overnight, double-bagged and temperature-protected with a heat or ice pack as needed for your destination.

Florida orders under $299 ship for $25; out-of-state orders under $299 ship for $40. Orders over $299 ship free. We don't currently ship to Alaska, Hawaii, Puerto Rico, or outside the continental U.S.

Free in-store pickup is always available — contact us for details.

If your coral arrives dead on arrival (DOA), report it within 2 hours of the delivery time shown on your FedEx tracking — email a clear photo to info@strictlyfishmiami.com and we'll issue a store credit for the purchase price of the livestock.

See our full Refund Policy for details.