Do Planted Tanks Need Filters

Angel fish roaming around planted tankPlanted tanks are aquaria that contain plants in the substrate, usually secured to rocks or some other material. Planted tanks can be described as miniature ecosystems; they support many small invertebrates and fish, contain snails and shrimp, and have complex nutrients that cycle through the system.

Planted tanks should have some filtration system to maintain good water quality. They can be broadly split into two types: active and passive filtration systems.

Active Filtration Systems

Active filtration systems are usually power filters, which you connect to the tank and keep inside. They use a pump to suck water through the filter material and then push it back into the tank through an outflow tube. These systems should be kept running continuously unless they’re being cleaned or serviced and require relatively high maintenance levels.

Active filtration systems are popular because they’re cheap, easy to use, and clear water. Under gravel, filters fall into this category, as do filter cartridges that sit in-between a cover and a tank base. Most canister filters would also be placed here. If you have a small planted tank without complicated demands on the water chemistry, then you might want to look at getting an active filter.

Passive Filtration Systems

Passive filtration systems are usually more straightforward equipment that doesn’t need electricity. Instead of using a pump to suck water through the filter media, they rely on gravity or simple siphoning to draw water through the material. These tanks can be big enough for one person to sway in the water easily: the most famous example is a bogwood and stone tank. They’re not suitable for keeping fish that will try to escape; snails need to be discouraged with rocks or other covers, and they don’t keep equipment inside, so you can’t perform maintenance when needed.

Which Filtration Systems to Use

If your tank has any of the following features, you should consider either passive or active filtration.

-It’s small, for example, it’s no more than 20 litres in volume (like a 10L Betta tank), and it contains few fish

-It’s heavily planted and has many snails or shrimp

-You want to keep delicate, fussy fish like some of the fancy goldfish

-You plan on regularly performing water changes (in which case you can use a bucket as your filter)

If you choose active filtration: 

-You should try to get a filter with a minimum turnover rate of 4 times the tank volume per hour. This is because small tanks have high water surface areas in proportion to their volume; for example, you might have a 10L tank that’s filled with bogwood and 3kg of gravel, giving you only 0.3 litres of “good” water to play with.

-You should get a filter that has other beneficial features, such as a quick-release cover. This will make it easier for you to siphon out detritus and check on your plants occasionally without disrupting the tank too much.

If you choose passive filtration: 

-The ideal tank would have a high surface area for maximum oxygenation; the size of the tank would depend on how many plants you have, but try not to get anything smaller than 20 litres.

-You should also place your bogwood and other decorative items so they can be moved around easily. This will make it even easier for you to siphon out detritus and check on your plants.

-The best tank for this kind of filtration would have a hood to stop debris from escaping or invertebrates climbing out. You can try sliding another lightweight plastic cover between the original one and the tank; that way, you won’t need to remove it altogether when checking up on your tank.


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