Over time, sponge filters collect a lot of detritus and dirt floating in the water. They should be cleaned roughly every couple of months, or when you notice your water quality is getting foggy.
- Turn off the filter pump and remove the sponge
- Put the sponge into a jug or bucket
- Collect some old tank water into another jug or container
- Pour just enough water over the dirty sponge to cover it
- Knead and rub the sponge together, pushing all the dirt into the water
- When the water is a solid brown colour, remove the sponge and pour the dirty water away
- Repeat steps 4 to 6 until the water is clear
Turning off the pump should prevent shrimp getting sucked into the filter whilst the sponge protection is gone. Be careful to check they haven’t sneaked inside before you put the sponge back and turn the pump back on.
Using old tank water from a water change helps to keep the beneficial bacteria living in the sponge happy and healthy during this process. The dirty water that you get from squeezing the sponge is great for watering your houseplants, they’ll appreciate the extra nutrients.
A double sponge filter is very handy here, as it lets you remove and clean the sponges one at a time without having to worry about losing the beneficial bacteria. You can just put back the first cleaned sponge and clean the second one a few days later.
You can always test your water for ammonia and nitrite a few days after you’ve cleaned the sponge to check your bacteria’s still thriving and working hard. In the worst case scenario, you could add bacteria in a bottle or seed it again with filter media from another tank.
Before & after
The before image shows the water quality before the sponge filter was cleaned, and the after image shows the same tank a couple of days later. The water will normally look much clearer within a few hours, you won’t need to wait days to notice a difference.
The clean sponge is so much better at collecting and holding onto the loose particles floating around the water.
Why it’s important
A dirty sponge filter is a lot less efficient at keeping your water clean and clear. This is especially true with a Hang On Back filter (HOB) - an inlet sponge clogged with dirt could wear out the water pump if not enough water can get through quick enough. The reduced amount of water flowing through the filter media will make it less effective at both biological and mechanical filtration.
However, you should be careful to clean the sponge properly, or you could risk crashing your tank’s cycle. The cleaning should only remove the loose dirt trapped in the sponge, without killing the beneficial bacteria. These helpful bacteria will maintain the ammonia at safe levels, keeping your shrimp healthy and happy.
If you notice the sponge disintegrating during the cleaning steps, you should replace it with a new one instead. You can keep the old sponge in the tank to seed the new sponge with bacteria, but you won’t want tiny bits of foam floating through your tank forever.
If you find yourself having to clean your filter sponge quite often, it might be worth checking if your substrate needs vacuuming.
The lightweight detritus and waste that sits on the floor can be easily kicked up by a shrimp swimming nearby, eventually ending up pulled into the filter sponge and clogging it up.
Washing with tap water
Never use tap water to clean your sponge filters, as you risk crashing your cycle by killing off these bacteria. Almost all tap water will contain chlorine / chloramine which is used to kill off bacteria in water, we obviously don’t want that affecting our colony of helpful bacteria.
If you don’t have access to enough old water, like if you’ve only got a nano tank, then you can use tap water if you condition it first with a dechlorinator. However, it will always be preferable and safer to just use old water.
Using soap to clean your filters is a terrible idea for the exact same reasons as using tap water. We only want to rub away the loose dirt clogging up the pores of the sponge and leave as much of the beneficial bacteria living in there as we can.
Soap will kill off all the bacteria and likely your shrimp too if it’s not completely removed from the sponge.