One of the most important parts that holds an aquarium together is silicone adhesive. If you need to repair or build a tank, you need to know what is the best silicone for your aquarium.
When we are talking about aquariums, we mean glass aquariums, which is what silicone is used for as a great adhesive. This is not for acrylic tanks.
The best silicone is strong, has high tensile strength, has no additives, and it has a good reputation among experts.
There is a lot of confusion around this topic, so it is best to understand as much as you can. Doing silicone work on a fish tank can be a huge time investment, so it best to do it right the first time. Also, using silicone incorrectly, may cause problems done the road with your display tank. You don’t want leaks, and you definitely don’t want your tank falling apart when it is filled up.
The main things to understand are how to apply, how long to cure, and how to test. You can have the best silicone in the world, but if you don’t apply it correctly, it doesn’t matter how good it is.
What Are The Best, Safest, And Strongest Silicones That Are Aquarium Safe
Momentiv RTV108
When I built a 130 gallon tank, which silicone did I use? I used Momentiv RTV 108 which is a clear adhesive, but it also comes in black if you need that color. If you ask around and do a lot of research, one of the most common used is this brand. It is also believed that some tank manufacturers use this brand as well.
This has better tensile strength over consumer grade silicone like what you would get at a big box home improvement store. If you take a look at its reputation online among aquarium builders, it has a solid one.
If this had a bad reputation, you would certainly know about it due to wide availability of information (especially negative) on social media and the interwebs, but the reviews on this are very, very good.
What makes this highly regarded by aquarium enthusiasts is its reputation. There are a lot of people using this silicone to build massive reef tanks, and they report it holding up extremely well for years. Whether it is saltwater fish only, freshwater, or coral reef tanks, this seems to be the most popular choice.
Also, it is pure silicone, and there are no additives in it like mold inhibitors, etc. Plain silicone is the best option for your tank. This comes in a small size tube as well as a bigger size that is used in a caulking gun.
What does RTV mean? It means Room Temperature Vulcanising
Some of the benefits are:
- Capability to cure at room temperature and ambient humidity
- Excellent weatherability and ozone and chemical resistance
- Self adhesion properties
- Low temperature flexibility
- You can buy it on Amazon
GE SCS 1200 Silicone
This seems to be the 2nd most popular silicone for aquariums. It has a little better tensile strength than the Momentiv, but not quite as popular. This is listed as a construction adhesive
You should be fine with either of the top two choices, and I would have no issue using this GE. This is a much better choice over the consumer grade versions you see locally in stores.
ASI Aquarium Sealant
For people who like the security of labels, this is a great product for you. This is 100% silicone designed for tanks up to 750 gallons.
There are tons of reviews for this on Amazon which is also a factor for a lot of people. It is really helpful to read positive results about a product in a similar application.
Marineland Silicone
Some people are just more comfortable with warranties and labels. If that is the case, this is for you. This is advertised specifically for fish tanks, and it even says it right on the bottle.
There are a lot of complaints about this brand, but that is because there is a foil sealer on the inside. So, when you try to squeeze the tube with a caulking gun, it may leak out the back. After you cut the tip off, just puncture the foil sealant, and then your caulking gun will work just fine with this.
The negative reviews that I read are regarding the foil, not the actual product failing. As you can read, there are tons of positive reviews based on the actual efficacy of it.
Aqueon Silicone Sealant
This is perfect for smaller jobs. Maybe you need to install some baffles for your sump, or a small repair.
This comes in a 3 ounce tube, and is less costly than the tubes for your caulking gun. You can get it in the bigger size, but it is usually more expensive than some of the other recommended products.
Also, this is labeled as ‘for aquariums’ which is a big appeal for some people, and some people don’t mind paying a few extra bucks for something labeled that way.
Are All Silicones The Same For Your Tank?
Well, not all silicone is the same. Some have additives that help reduce mold and mildew, and since we are dealing with water and moisture, that may sound like a good idea, but it may not be great for the living creatures swimming and breathing in it every day.
Some have UV protection which may be great for your home exterior, but not necessary for your tank. Again, those are added chemicals, and we need just pure silicone.
They all may have different cure rates. While having one that cures fast seems great, but is a faster cure better than losing adhesion strength? No it is not. As we have said many times before, if you are not a patient person, then this hobby is not for you.
Faster cure times are great for your patience, but it may also cause poorer adhesion between the glass and the seams. This is not something you can risk.
Some have additives that allow it to be painted after cure. This means that it is not 100%, and it contains other chemicals in it. This may make it have less adhesion, or it may make it toxic to livestock.
Why do some say Aquarium safe and others don’t? There is probably a legal reason or marketing reason for that. Silicones that are not marked ‘safe for aquariums’ on the exterior of the package have been used for years in building tanks. Having said that, there are many consumer grade silicone products that do not say that either, and they should not be used for your tank.
If you prefer the safety of the label, then we have a couple on this list that are great choices.
Tips For Using Silicone In Your Aquarium
- Do not apply new silicone over old. It works by adhesion to the glass surface. If the glass surface is fully or even partially covered, that is less area for it to bond to the glass.
- If you are building a tank or replacing a glass pane, make sure to use the larger size that works with a caulking gun. You will be very frustrated trying to do a big job with the smaller size tubes.
- Do not buy marine grade that is for boats and RV’s. That is designed for boat structures, not glass adhesion.
- Watch plenty of videos and read up on the best way to use this in your tank. You do not want a mess on your hands down the road when you could have spent an hour or so more learning about better technique.
- Silicone is not the best for acrylic aquariums. You would need Plexiglass or PVC cement which bonds acrylic together.
- Do not rush into adding water in your tank. It needs time to cure. Some tank builders recommend waiting one to two weeks depending on how thick the bead is. Not letting any silicone cure fully will release toxic chemicals into your water and it will kill everything. Better to be over safe then sorry later.
