Back to Back Issues Page
The Goldfish Gazette, Issue #026 -- Sponge Filters - Are They Underrated?
February 28, 2016

Goldfish Care Tips and Guidelines

A Free Monthly Resource For Goldfish Enthusiasts
February 2016
Issue #026

In This Issue
Sponge Filters - Are They Underrated?

Sponge filters are the ideal filtration solution for the Goldfish fry aquarium because they don't suck up the fry or the live food they are being fed.
But do they have other applications?

Sponge Filters - Are They Underrated?

I am the first to admit that apart from fry aquariums, I considered sponge filters too inefficient to be of any use anywhere else in my setup because Goldfish are messy creatures that produce a lot of waste.

But then I came across a website that not only sold sponge filters, but claimed they were more efficient than hang on back (HOB) filters and most canister type filters.

The timing couldn't have been better as I was about to reinstall a large canister filter outside for my ponds which are set up on 3 levels.
Water is pumped from the lowest pond up to the top pond where it overflows back down again, similar to a water fountain system.

The problem with this system is all the ponds are linked, so if there is a disease or water problem in one pond, it quickly spreads to all ponds.

During the breeding season the system has to be shut down because the water levels need to be lowered and there can’t be excessive water movement during spawning.

The ideal solution is to have a filter in each pond, but that requires power leads to each and either an external canister filter with associated hoses or an internal power filter installed.

But what about sponge filters?

How They Work

An air line is attached to the filter. As the bubbles produced rise to the surface, they create a small vacuum which sucks water through the sponge material, up the central uplift tube and back into the water column.

Nitrifying bacteria build up in the sponge material and process ammonia and other water impurities as they do in any filter.

Filters that use a water pump are generally more efficient because they move more water volume, but sponge filters are also capable of moving large amounts of water, especially when a power head is attached.

It is a combination of water volume through a filter, and the amount of filtering media in the filter that the nitrifying bacteria can populate that measures efficiency.

By design the major part of a sponge filter is filtering media.

Advantages of Sponge Filters

  • Cheap to buy
  • Simple construction
  • Easy to clean
  • Agitate the water surface without creating a strong current
  • Safe to use outside (no power leads).

Disadvantages of Sponge Filters

  • Unsightly (in a display aquarium)
  • Take up space in the aquarium/pond
  • Tend to clog easily in heavy waste environments
  • Other filtration media can’t be easily placed in the filter
  • Air volume required for larger sizes to achieve high water flow
  • Can float to the surface.

Match Sponge Filter Media To Your Setup

Most sponge filters sold in pet shops have a fine sponge material which quickly clogs in a Goldfish environment. An American Company Aquarium Technology Inc produces a sponge filter in 5 sizes but with three different sponge densities:
1. Hydro-Sponge which is a fine media density suitable for most applications with low waste environments
2. Hydro-Sponge pro which is a coarser media which resists clogging in applications where higher water flow rates are required such as for larger aquariums and heavy waste environments such as a Goldfish aquarium
3. Hydro-Pond which uses a coarser media again for the pond environment.

Long Term Pond Test

I am running a long term test in my small outside ponds with four Hydro-Sponge pro filters I purchased from American Aquarium Products.

You can probably purchase these filters from other sources but they were so cheap and this website has extensive information on these filters which is well worth the read before making a final decision.

So far I have found that if they are put into a pond with green water, without first populating them with aerobic bacteria, they are so efficient they suck up the alga which then causes the filter to float to the surface. I have weighed these filters down with flat rocks around the bases to see if they can clear the water of algae.

These filters don’t come with air stones (diffusers), they rely on a simple splitter at the top of the filter to break up the air flow into bubbles. They do have provision under the splitter to fit an air line with an air stone for increased water flow. I have fitted air stones to all the filters.

To read more about filter options for Goldfish click here...

Comments? Ideas? Feedback? I'd love to hear from you. Just reply to this e-zine and tell me what you think, or what topics you want covered.

Next Month's Topic

Culling fry to produce champions

Back to Back Issues Page