Changing Gravel in an Established Tank – Safest Ways To Change Or Replace The Gravel In Your Tank!

If you’re thinking about changing gravel in an established tank, it’s essential to do it in a way that won’t end up overly stressing or even killing your fish. The best way to change the gravel is not to just scoop out the old gravel and pour in the new.

Read on to discover the safest way to add new gravel or sand to your fish tank without sacrificing the good bacteria that your tank needs to keep everyone healthy.


Replacing or Changing Substrate in an Established Fish Tank

Replacing or changing substrate in an established fish tank involves a process that requires a little planning for the best and safest results.

Is It Safe to Change Gravel in a Fish Tank?

If you have had your fish tank set up for a few months or even years, your gravel will contain a lot of good bacteria, which is necessary for the health of your tank. Also, remember that the filter, plants, and decorations in your tank also contain essential bacteria.

If you remove all the gravel from your tank at once (especially if you also remove the decorations), you will upset the normal nitrogen cycle in your tank. This upset can cause the ammonia and nitrite levels to increase to dangerous or deadly levels in your aquarium.

There are four options for changing gravel in an aquarium with varying levels of safety:

  1. Gravel Seeding (Safest): After you rinse your new gravel, place it in pantyhose or filter media bags and put them in your aquarium to culture bacteria. After a month, the new gravel will be ready to replace your old gravel.
  2. Fishless Cycle (2nd Safest): Add the new gravel to a fishless tank, and place it through the cycling process. After the tank is fully cycled, your new substrate will have good bacteria on it already.
  3. Replacing Sections (3rd Safest): You can put a divider in your tank and change a few sections at a time to keep the bacterial benefits from the old gravel while you change. Wait a month between sections.
  4. Adding Fresh Gravel (Least Safe): Rinse the new substrate and add it to the tank.

Should You Replace Gravel in a Fish Tank?

There are only a couple of reasons to replace gravel in your fish tank:

  • Aesthetic: You might decide to replace the substrate if you want a new look or theme for aesthetic purposes.
  • If you made a substrate mistake for your fish type: Replacing the gravel in your fish tank may be necessary if your research revealed you chose the wrong substrate for your fish (like using gravel for a Mbuna cichlid instead of sand or cichlid substrate).

How Do You Remove Gravel from a Fish Tank?

To do a complete gravel change, you will want to follow these steps:

  1. Test your water: You will need to get the ammonia and nitrite levels to zero before you make a change that will result in chemistry spikes in your tank.
  2. Don’t clean your filter: If you have changed or cleaned your filter, you will need to wait a few days to allow bacteria to accumulate on it again.
  3. Don’t feed your fish the day before: Not feeding your fish will reduce the amount of waste in the water that can raise ammonia and nitrite levels.
  4. Turn off your filter.
  5. Siphon water from your tank: Transfer water to a nearby 10-gallon tank or 5-gallon bucket. You will use it to hold your fish and decorations during the change.
  6. Remove your fish and decorations: Transfer your fish and decorations to their temporary holding tank or bucket.
  7. Remove the old gravel: Scoop the old gravel into a container.
  8. Vacuum: Vacuum and debris remaining at the bottom of the tank.
  9. Add the new gravel.
  10. Replace your decorations: Place any rocks, decorations, and plants back in your tank.
  11. Top off the water. Adding freshly treated water rather than old water to the tank will help with ammonia and nitrite levels.
  12. Turn your water filter on again.
  13. Add the fish back into the tank.
  14. Watch for spikes: Test the water often for the next week or so, and do a partial water change if you detect any spikes in ammonia or nitrites.

How Do I Add Gravel to an Existing Aquarium?

If your new gravel isn’t in water, the easiest way to add it to a new aquarium is to scoop it out with a cup and place it in the aquarium a little at a time. However, if you have it in another tank for cycling, you can use the water bottle method.

Water Bottle Method

The water bottle method is an effective way to move gravel from one tank to another:

  1. Scoop gravel into a clean water bottle.
  2. Partially cover the bottle opening with your thumb and flip the bottle over to allow the bottle to fill the rest of the way with water.
  3. Carry the bottle of substrate and water to your main tank.
  4. Turn the bottle upside down inside the water to allow the substrate and water to flow easily to your desired spot.

Can I Put New Gravel Over Old Gravel?

Putting a new layer of gravel over old gravel is safe and possible. You can use it to help protect rooted plants, make a new look, or add depth to your existing substrate. Plus, you keep all the good bacteria in the tank.

Changing Gravel to Sand in an Established Tank

If you want to change gravel to sand in an established tank, it’s essential to do it all at once rather than mix gravel and sand.

Here are the steps for switching from gravel to sand:

  1. Turn off your filter.
  2. Siphon water from your tank into your fish holding tank.
  3. Remove your fish and decorations to the temporary holding tank.
  4. Place the old gravel in mesh bags.
  5. Vacuum debris from the bottom of the tank.
  6. Add the sand.
  7. Add decorations and gravel bags back in your tank.
  8. Top off the water with freshly treated water.
  9. Turn your water filter on again.
  10. Add the fish back into the tank.
  11. Remove the gravel bag after one month.

Video: Switching Your Aquarium Substrate From Gravel To Sand!

How Often to Change Gravel in a Fish Tank

Changing the gravel in an established tank is not something you should do regularly. However, it is vital to keep your gravel clean. Always place your vacuum hose deep into the gravel when you do regular water changes to remove food and waste that has collected there.

Jack Dempsey
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