6 features of an ideal planted tank filter

Plants filter the water no? Why is a filter still useful in a planted aquarium?

Mature planted tanks with a low ratio of bio-load to plant mass may not require much biological filtration for ammonia from livestock, as growing plants readily take up ammonia as a nitrogen source.

However, ammonia is not the only form of organic waste in a tank. High-density, high-growth tanks that are pruned and replanted frequently often produce a lot of organic detritus from cut plants and old growth, even without much livestock. These become a trigger for algae even when water parameters show no ammonia. Planted tanks that are slower growing (i.e. low tech/non CO2 style) actually produce less plant detritus in comparison.

To this end, filters are still extremely useful in planted tanks to trap plant debris and process organic waste - the main algae triggers. One of the most useful features of a filter is therefore the ability to remove coarse organic debris on a regular basis. This section also covers other features that are important in a filter. Features such as ease of maintenance should not be underestimated, as this will have a major impact on whether a person will actually carry out regular maintenance on the filter or put it off because of the hassle of dismantling parts of the filter.

One the filters that we use extensively is the Oase Biomaster series. (featured in top picture) Here we go over key features that I think should be in every filter setup.

6-10X Turnover flowrate

For many planted tanks, the filter is the main source of water flow. A good filter size, and therefore flow for the tank, eliminates the need for additional pumps or additional filters. This means less visible clutter and fewer filter inlets/outlets to detract from the aesthetic beauty of a clean set-up.

In a planted aquarium, a flow of around 6 to 10 times the turnover of the tank volume is our recommended 'target' flow rate to achieve optimum circulation of O2/CO2 - and to deliver nutrients to the plants. Of course, the filter should operate with minimal noise, and the better ones do this with ease. In other words, strong AND quiet flow is achievable, widely available and should not be compromised.

We prefer to use a single filter for tanks of 4ft and below, without additional pumps. The use of glass tubes, which are easily concealed, further disguises the presence of tank equipment.

Heater Slot

Less equipment in the tank maximises space for aquascaping. Being in the centre of the flow ensures that heated water is evenly distributed throughout the tank. Less clutter in the tank means a cleaner display and more room for aquascaping.

Priming Mechanism

There is often the misconception that a filter is set up once and left to run 'forever'. This contributes to algae problems, especially in heavily planted tanks. To make the chore of regular maintenance less onerous, easy accessibility is key. A priming function enables the starting of the filter without the need to manually start the downward flow of water in the filter intake pipes. (i.e. sucking on the water hoses). It enables far easier maintenance work and setup if the filter require priming to start up again. Most modern filters have this by default.

For filters such as the Oase biomaster series, filter maintenance is further improved by having an easily removable pre-filter compartment as detailed below.

Removable pre-filter

Easy access is the best way to encourage regular maintenance and tank cleanliness. Nothing helps this more than a pre-filter compartment that can be cleaned without dismantling the main filter. Planted tanks produce a lot of debris that needs to be removed regularly. Having an easy access system makes tank maintenance much easier. We feel this is an essential feature that is often overlooked. Many filter models do not come with this - the two models we use that do are the Oase Biomaster range and the larger filters from Aquael.

The fine filter sponges on the Oase Biomaster are designed to trap fine debris; this means that the main chambers remain very clean. The downside is that they need to be emptied more often; we clean my pre-filters every 3 weeks to a month depending on the tank setup. We only service the main chambers once every 6 to 8 months.

The Oase Biomaster series have a sizeable removable pre-filter compartment.

Quick release valves

This allows the filter to be serviced without fumbling with the water hoses. Quick-release valves allow the filter to be removed from the water lines leading into the tank immediately without any messy/dripping water. It is easy to install your own valves if the filter is supplied without them.

Build-Quality

Filters will last a long time if they are made from good quality materials. Low quality models are more likely to leak and break down.