ASI 509 Aquarium Silicone Sealant, Black, 10.2 oz Cartridge

Black aquarium silicone from ASI is the black version of ASI 509 Aquarium Safe 100% RTV Silicone, the sealant American Sealants Inc. makes for aquarium manufacturing and repair. It shares one data sheet with the clear version (520 psi tensile strength, 500% elongation, primerless adhesion to glass) but outlines each seam in black instead of hiding it. Pick black when you want a framed, defined edge or when the tank sits against black trim, a dark stand or a black background.

Key features

• Opaque black seams with the same published strength figures as clear ASI 509
• Rated aquatic-life safe once cured, for fresh and saltwater aquariums
• High tear strength (45 lbs/in, Die B) and 45 Shore A cured hardness
• Held 203 psi lap shear after 300 days underwater, failing cohesively rather than letting go of the substrate (ASTM C-961)
• Meets FDA 21 CFR 177.2600; VOC compliant
• 10.2 oz caulking cartridge, non-slump for vertical and overhead seams

Where to use it

ASI’s applications are aquarium manufacturing and repair, terrarium manufacturing and repair, glass viewing panels, and sealing or bonding aquarium filters. Black is a natural fit where the seam meets a dark background, an overflow box or a filter compartment, or on display tanks where a crisp black outline is part of the look.

How to use

1. Plan the seams first: black shows every wobble, so mask both sides of each joint with tape.
2. On repairs, remove the old silicone completely; then clean the glass with 100% isopropyl alcohol or acetone and let it dry. No petroleum-based solvents.
3. Gun a continuous bead between -35°F and 150°F, then tool it and pull the tape within about 10 minutes, before skinning.
4. Ventilate while it cures; the acetic acid (vinegar) odor is normal for this acetoxy silicone.
5. Leave the tank dry for the full 7-day cure before adding water or livestock, as ASI recommends.

Compatibility and cautions

ASI lists glass, most acrylics, aluminum, metals, steel, porcelain, PVC, most woods and some plastics. It should not be used on porous surfaces such as concrete, mortar or brick, and it cannot be painted, so choose the color before you start. Cold temperatures and low humidity slow curing. The SDS does not classify the product as hazardous under GHS; use it outdoors or in a well-ventilated area and read the label first. Shelf life is 12 months at 70°F and 50% RH. Documents: technical documents.

Choosing between black and clear, and other ASI sealants

For seams that should all but disappear, use ASI 509 clear aquarium silicone. General-purpose black ASI 502 looks similar in the tube but is not aquarium-rated, so keep it for trailers, trim and metal work. More about the brand in our ASI silicone sealants overview.