Exact Answer: 24 to 72 hours
Avid fish lovers are conspicuously aware of the need to maintain a well-furnished and well-kept aquarium. It is important to check the aquarium regularly to detect any possible leaks or compromised seals. When new leaks start developing inside an aquarium or old seals begin to wear off, resealing them becomes essential.
This is done by using a silicone sealant. There are some other important tools needed to seal an aquarium including acetone, and razors or sharp tools to scrape off the old sealant. The sealant selected to fix the leaks must be waterproof and non-toxic so that it does not affect the health of the marine life living in the aquarium.

How Long To Wait After Sealing Aquarium?
Sealing an aquarium is a task that can test the patience of an individual. When a silicone sealant is used to fix leaks in an aquarium, one must be ready to wait for a stipulated time frame for the sealant to dry and the fish to be restored in the aquarium environment. If this waiting period is not diligently followed, it can affect the health of the fish as well as reopen the leak.
When understanding how a sealant dries, it is important to know that there are three different levels included in the drying process. The sealant will start to ‘feel’ dry within the first few hours of its application. Although the sealant layer is set with the first 24 to 72 hours after its application, it dries out completely only after a week. If you wish to wait for the sealant to completely dry out, you may need to wait for 4 to 7 days.
Similarly, you can use certain catalysts to hasten the process of drying. Using blow dryers or a heat lamp can accelerate the drying phase. In such cases, it is possible to dry the sealant within 48 hours of its application.
If the work done on the aquarium is minor, it is not necessary to wait for 4 to 7 days. The small proportions of sealants will optimally dry within 2 days. Moreover, different sealant companies specify different timeframes of waiting. The best way to approach this process is to stick to the guidelines specified on the product itself.
In the long run, the sealant will only completely lose moisture and dry thoroughly after a week. However, it is possible to use the aquarium after the first 3 days. This implies that the marine life can be re-transferred into the aquarium after this minimal waiting period is over.

In Summary:
Drying Speed of The Sealant | Waiting Time |
Hastened Drying (By Using Blow Dryers) | 24-48 hours |
Normal Drying (Set Sealant) | up to 72 hours |
Complete Drying | 4 to 7 days |
Why Do You Have To Wait This Long After Sealing Aquarium?
Silicone sealants take time to dry. If the sealant comes in contact with water before it can completely dry, the sealant bonds will become weaker and in turn, take longer to dry. The efficacy of the product will inevitably be lowered in such cases. You can expect the sealant to scrap off and open up the leak within a few weeks.
Once the chalk in the sealant gets wet before it can dry, its integrity and effectiveness are compromised. Moreover, this can cause the growth of moss and molds in the sealant bonds, which can be detrimental to the health of the marine life stored inside the aquarium.
In a hot and dry environment, the process of drying is accelerated. Thus, the sealant can dry properly within a day or two of its application. However, if the weather is humid and heats deficient, it will take the sealant longer to dry.

Blow dryers and heat lamps evaporate the moisture from the sealant faster due to the concentrated nature of the heat they provide. This aids in reducing the time needed to ‘naturally’ dry. However, this process of drying has a caveat too. Direct heat is not recommended for sealants. If you happen to use a heat lamp, keep it at a conducive distance from the sealant for best results.
The vinegar smell test is the most commonly used test to determine if the sealant has dried. Since a silicone sealant releases acetic acid when it starts drying, when this smell stops, it is prudent to assume that the sealant has dried optimally.
Conclusion
Aquariums serve as a wonderful medium to appreciate marine life. They help add both aesthetic value and a conservative spirit to a room. However, often there are leaks along the walls of the aquarium that can cause severe damage to the fish inside. It is important to swiftly detect the leaks and fix them.
Silicone sealants are generally used to fulfill this objective. The sealant is left untouched for at least 24 to 72 hours after its application. Usually, the formula optimally dries within this time period and the marine life of the aquarium can be restored. However, it takes the sealant about a week to completely dry out and form a strong bond with the aquarium walls.
References
- http://krishi.icar.gov.in/jspui/bitstream/123456789/25314/1/Extension%20Folder%20No.%2072.pdf
- https://www.sciencedirect.com/science/article/pii/S0045653510007320

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