If you are interested in a small aquarium filter then you can check out this one: Rio Mini Internal Power Filter.
It is a good and inexpensive small fish tank filter, properly for tanks that are up to 40 gallons (perfect for 30-40 gallons). A good thing about it is that is very cheap but resistant
compared with other categories filters that look- a-like. It filters about 85 gallons water per hour. This filter, although seemingly complex, it’s easy to install, also does not consume much energy and it’s a perfect underwater aquarium filter.
Everything you need for installation it’s contained in the kit box. This internal filter aquarium has two internal compartments based sponge filter, but you can replace without any problem one of the compartments filter sponges with charcoal for freshening the water. With more positioning options this filter can be mounted vertically and horizontally in your aquarium, without taking up too much space and without being noisy (efficiently for use in nursery–aquariums type). This product it’s very powerful for its size, it’s also a saltwater fish tank filter and a freshwater fish tank filter. Rio Mini internal power filter comes equipped with a variety of accessories, but some of the most important being a joint in right angle and as well a spherical joint. Water flow that pump realizes it’s a major one, but can be easily adjusted, depending on tank capacity and the level of filtering that you need or fish that you have on your aquarium.
Overall, this filter is easy to use with interchangeable different options, occupies a small space in the aquarium and it’s inexpensive. You should keep in mind that different media that you will want to change are sold separately and they require also those nylon bags which are also sold separately.