Daily Questions

Daily Question: What filter do I need?

John asks, What filter would I need for a 5 foot by 1 and a half foot by 2 foot tank?

Your tank is about 400 litres, so you will need a decent filter. Filters are measured in how much water they can push through them in an hour, but this is without media in them and often at a lower height between the filter and the tank than we really use them at.

Types of filter

There are three main types of filter, internal, external, and sump, but there are also a lot that have either fallen out of fashion, or are more specialist, such as under-gravel filters, hang-on-the-back (HOB), sponge filters, and various types of built-in filters, but they all operate in the same way. Water is pulled through media, often mechanical in the form of sponges, then biological, which is often ceramic or similar to give a huge surface area, and for some chemical media i.e. carbon.

Turnover rate.

Turnover rate is the number of times that the water is drawn through the media and back into the tank per hour. For example, if you had a filter with a true turnover rate of 2000l per hour, your tank would be seeing a turnover of 5 x per hour.

At a minimum, you should be looking for 4 x turnover per hour, but up to 10 x per hour is often recommended.

Internal, external, or sump.

I would discount an internal filter. The Juwel Biofilter XL claims to be suitable for up to 500l, but at rating of 1000lph I suspect it will struggle in anything but an understocked tank. I am a huge fan of these filters, but I don’t think in this case it’s big enough.

So that leaves you with either a sump or an external. A sump is always a great choice, but you need to either be confident to make your own or get one custom-made. Then you need holes in your tank and weirs to prevent all the water from draining out in case of a power failure.

The most practical option is an external filter. I’ve listed three options below.

Oase BioMaster 600 External Filter

A filter that satisfies my love for an easy-to-clean filter, a built-in prefilter that can just be pulled out, cleaned and replaced without touching the rest of the media. The Thermo will include a heater, which is a great way to keep you and your fish that bit safer. I would still run a thermostat to for that extra piece of mind though. If you want German engineering and all the bells and whistles this is the one to go for. Plan to clean the prefilter weekly and you will have a great filter.

Check out the offers here from Maidenhead Aquatics.

Or grab one here from Amazon

Fluval FX series

Hands up my main tank is running an FX5, I have managed to kill one that was at least 15 years old. But this one we are pretty sure is approaching 20 years old. I say we as I borrowed it about 10 years ago, and have yet to give it back. Want a relatively straightforward filter? This is the one for you. Big baskets of foam and bio media, the top tightens down with screws, turn off the water from your tank and very little if any escapes. Self-priming and if you want you can drain it from a tap on the bottom. Yes I can pick small issues, but I am a fan of these beasts. Bob Mehen once described them as a squat R2D2 squatting under your tank, and he’s not wrong. They don’t normally come with enough biomedia so add in a bag of alfagrog.

Buy the FX4 here from Maidenhead Aquatics

Grab the FX6 from Amazon

Dont forget the Alfagrog

All Pond Solutions 2000L/H EFX+

Before I write this bit be aware I have used so many APS filters, but my overwhelming opinion is, a cheap filter that will do. But fishkeeping should be fun and priming an APS filter after wrestling the clips into place, and making sure the UV is in the right place, pushing the clip into place, is not fun.

Eventually, the clip for the pipes at the top will break, the bucket itself will warp, and everything will start leaking, you can add a few more years by adding a better o-ring, but the price point is far lower than the other two. I’ve had one of the larger APS for 7 years until I came into the fish house to find the water jetting across the room as it drained a tank for me. Would I recommend one. Yes if you’re on an extreme budget, but get the prefilter to pop in line and clean that weekly to avoid fiddling around with the main filter itself.

Buy here from Amazon

Your other option if you are on a budget is to build an internal filter in your tank. It would take a whole article to itself, but in short you can section one end of the tank and use a pump or power head to pull the water through media, over and under baffles.

I can’t say what your budget is, but I know that once this FX5 finally dies, and it’s making that sort of noise now, I will be buying a new FX6. However, when I replace this tank I will be getting the new one drilled and set up for a sump.

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Ruth McDonald

Sailed twice around the world, started my acedemic career as an archaeologist and somehow ended up lecturing on science and researching fish.

Tropical Fish Keeping UK