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I recently bought a used 100 gallon aquarium on craigslist. This tank is drilled with an overflow for a sump, and was previously used as a saltwater reef tank. I like running a sump on my larger freshwater aquariums, so this tank will be a planted freshwater rainbowfish display. But before I can fill it with water, I'm going to have to clean and reseal it.

Dirty Used Tank
Dirty Used Tank

Why reseal an aquarium?

You would want to reseal your aquarium if either: 1) it leaks or 2) you suspect it may leak

When buying a used aquarium, you can't be sure how long the aquarium has been in use, or how it was stored. Even if a pre-owned aquarium does hold water, silicone seals don't last forever. After 10+ years, silicone will harden and shrink. Eventually, the tank will leak. Storing an aquarium outside or in a garage where it is subject to a wide range of temperatures will also weaken the silicone. Unless you're getting a gently used aquarium from a hobbyist you know, its wise to assume you'll need to reseal large secondhand tanks.

Can I just reseal one edge of my aquarium?

No. New silicone won't adhere to old silicone. The only way to properly reseal a tank is to remove all of the old seal and replace it.

Resealing an Aquarium

The process of resealing a used aquarium is simple, though it is very labor intensive. Expect this whole process to take you several hours. The supplies you'll need are:

1. Clean the aquarium and remove the old silicone

You need the aquarium to be completely clean to ensure a good seal. Vacuum it out, wipe all the gunk off the glass, and then start scraping off the old silicone. Be careful when scraping not to cut the silicone bead that holds the panes of glass together. You are just removing the seal on the inside of the tank, not cutting the panes of glass apart. In the photo below, the old seal has been completely removed.

Cleaned Out Tank
Cleaned Out Tank

2. Tape off the seams

After all the old silicone is removed, wipe the glass clean with some rubbing alcohol. Once it dries, apply tape around all of the seams. This will determine the outcome of your new seal, so take your time applying the tape. You should leave enough space so that your silicone bead will be at least as wide as the thickness of the glass. Use a razor blade to cut the tape at the corners so you get clean lines.

Taped Off Tank
Taped Off Tank

3. Apply silicone

Once the tape is applied, prepare your silicone and have rags ready. The silicone will begin to "skin" in about 10 minutes, so timing is important. Once you apply a bead of silicone, smooth it out using your finger or a tool for smoothing caulk. Then remove the tape before the silicone begins to set. In my case I worked my way across the tank in sections. I did one side panel, then removed the tape from that section before continuing. I recommend this approach on larger aquariums. The whole tank must be resealed in one shot. Once silicone dries, new silicone will not adhere to it.

In my case, this was a 2 step process. I resealed the aquarium itself, allowed the seal to cure, then added in the overflow. The photo below shows the finished tank.

Resealed tank
Resealed tank

Things to keep in mind when resealing an aquarium:

  • Silicone has a strong vinegar smell - make sure you work in a ventilated area
  • Wear gloves to keep the silicone off your skin, have rags handy to wipe excess off your hands
  • Don't worry about stray drops of silicone that get on the glass where you don't want them - these can be easily scraped off later, just let it dry

4. Allow the new seal to cure

Follow the instructions on the tube of silicone you're using. I recommend waiting at least 48 hours before attempting to fill the aquarium with water. You have nothing to lose by giving the silicone an extra day to cure. If it still smells like vinegar, its probably not cured yet.

5. Enjoy

Once the silicone is fully cured you can start the fun part: setting up your tank!

Newly scaped aquarium
Newly scaped aquarium

How to use potted plants in your aquarium fish tank
Potted Plants in an Aquarium
Potted Plants in an Aquarium

Why add potted plants to your fish tank?

Live plants come with a lot of benefits for your aquarium: they eat ammonia, they look better than fake plastic plants, they inhibit algae growth, and they create a more natural environment for your fish. More benefits of live plants are discussed in this post about pothos in the aquarium. But not every aquarium has a good substrate or the right conditions for planting live plants.

In breeding or quarantine setups you might want to run a bare bottom (like the tank pictured above). If you keep boisterous cichlids that like to dig, no plant is safe in a regular substrate. Maybe you need to be able to move plants around between aquariums easily. An easy solution in these cases is putting potted plants in your fish tank.

Lotus in a Shallow Pot
Lotus in a Shallow Pot

What kind of pots are safe for aquarium use?

The first step in adding potted plants to your aquarium is choosing the right containers. You have a lot of options here. Standard terra cotta clay pots, that are not painted or glazed, are safe for use in an aquarium. You can also use plastic plant pots, or upcycle any plastic container that is the right shape and size for your goals. A (thouroughly washed) yogurt container or plastic tupperware can hold substrate as well as any pot.

Various Aquarium Safe Pots
Various Aquarium Safe Pots

When choosing a container, keep in mind that some plants are heavy root feeders and will need some space for their roots to grow, while others can be planted in a shallow substrate. For example, java fern does not need any substrate at all, so you can use a very shallow pot to hold it in place. Plants like jungle val and amazon swords will want a deeper pot with a good quality substrate.

What substrate to put in aquarium plant pots?

Any aquarium substrate that you would use in your fish tank can work for potted aquatic plants.  For root feeding plants, I recommend using some organic potting soil (sift and rinse it thoroughly first) capped with aquarium gravel.  This will supply the plants with nutrients for years, while keeping them contained.  This method works particularly well for valisneria, which will quickly take over a dirted tank if not contained.  

Another option is to use regular aquarium gravel and add a few root tabs to the substrate to supply nutrients.  Aquarium Co-op sells root tabs and other planted tank supplies.  You can find root tabs on Amazon as well.  These will need to be replaced every few months for the best results, but luckily theyre cheap.

Root Tabs for Aquarium Plants
Root Tabs for Aquarium Plants

Rinse the pot or container before adding substrate.  If it has large holes in the bottom, cover or plug them with some plastic (like a bottle cap) or mesh before the substrate goes in.  This will prevent dirt or gravel from spilling out the bottom of the pot when it is lifted.  A few small holes in the pot's bottom is actually ideal for a lot of plants, because their roots will be able to grow out through the bottom and pull more nutrients from the water column.  

Potted Crypt
Potted Crypt

Adding your potted plants to your aquarium

Potted Plants Being Rinsed
Potted Plants Being Rinsed

Once you've chosen a container and substrate and planted your plants, make sure you rinse the plant and the pot in some fresh water to remove any dust from the substrate before adding it to your aquarium. The greatest benefit of potted aquarium plants is you can re-arrange them easily, moving them around as often as you want. Dont hesitate to try a lot of different plants in a lot of different configurations!

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You can easily run air to any outdoor pond or tub with this cheap combination of tools.

Solar Pond Air Pump

You can easily run air to any outdoor pond or tub with this cheap combination of tools. A USB powered air pump run by a small solar panel with USB outputs is all you need! The video below shows my setup running on my 100 gallon guppy tub - which you can read about here.

Setting up Solar Powered Pond Aeration

These little USB air pumps can drive a steady stream of air to the bottom of a 2.5 foot deep, 100 gallon stock tank. 

USB Nano Air Pump

Such small air pumps use very little power, so a single solar panel hung in a sunny spot can run one for most of the day.  While this setup won't provide aeration at night, it will increase air exchange during the hottest part of the day.  This helps prevent the tub from becoming stagnant and keep the water oxygenated for the fish.

Look for a cheap 20 watt solar panel - like the one shown below - that has USB ports as its power output. Then you just have to plug the air pump into the panel, and place it in a sunny spot. I hung my solar panel on the side of shed, and it powers the solar pond air pump for 10-12 hours a day during the summer.

Solar Panel / Air pump

Start backyard tubbing with your own 100 gallon stock tank! These are great for small outdoor ponds. The rubbermaid construction will last for decades, and they are much cheaper than a similar size aquarium.

Guppy Tub 2020
Guppy Tub 2020