What is Mulm or Detritus In Aquariums?


What is Mulm or Detritus in Aquariums?

Is there a brown or black substance that seems to collect like dust bunnies all over the floor of your fish tank? Mulm, debris, and other dirt-like substances are all names for this substance. It’s an important part of healthy aquariums. Continue reading to learn more about mulm, its composition, how to reduce it and whether you should get rid of it.

What is Mulm?

Mulm is made from fish poop and plant leaves. The decaying organics are broken down by bacteria, fungi, microorganisms, and tiny microfauna. This army of microorganisms transforms the organic matter into mulch, which is rich in essential minerals and nitrogen compounds. In fact, the fertile soil in our yards and gardens is basically mulm that is made up of decaying leaves, animal droppings, and so forth. Mulm is a kind of compost heap in an aquarium. It is where organic waste is transformed into rich nutrients that can be used for the revitalization of the substrate in which plants grow.

Is Mulm Harmful

You can generally say no, as long as there is enough biological filtration (e.g. beneficial bacteria and microorganisms), to safely remove the waste. An aquarium water test kit can help you determine the level of ammonia, nitrite and nitrate in your aquarium. Detritus buildup in your tank could indicate that you have too many nitrogen waste compounds. This can cause fish to become sick. Mulm can look like black or brown sediment. If you notice large amounts of uneaten food, or any other organic materials that aren’t being broken down, it is worth removing with a gravel vacuum. This will prevent dangerous spikes in nitrogen waste.

Mulm is good for planted aquariums, as they rejuvenate the substrate and provide nutrients for plants.

Although mulm might seem unattractive, it is actually a sign of a healthy ecosystem in your fish tanks that can sustain life and process organic matter without affecting the water quality. Because of their murky and muddy water, lakes and ponds in nature can appear “dirty”. The mulm that lies beneath these waterways is full of nutrients, which continue to feed the animals and plants living in them. In fact, some aquarium hobbyists encourage the growth of mulm by adding catappa leaves and driftwood to create a more natural-looking biotope or breed fish that like the additional cover.

Should You Get Rid of Mulm?

It all depends on if your aquarium can use it. Here are some options to think about:

Fish tank without live plants: Mulm may cause water to cloudy, especially for bottom-dwelling fish who like to dig in the substrate. The water will look clearer and cleaner if you remove excess mulm. – Fish tanks with live plants: Detritus is often left in the aquarium because it provides essential nutrients for plants to feed on and can potentially decrease the amount of fertilizer that is needed. However, if there is so much mulm that it covers your carpeting or short foreground plants, you may want to remove some of it to make sure the plants are getting enough light. – Fish tanks with fry: Mulm in an established aquarium often grows infusoria and other microorganisms that are an ideal first food for baby fish. Additionally, smaller fry will benefit from the extra debris.

An aquarium vacuum can be used to vacuum the tank’s bottom. This is because the heavier substrate sinks and the lighter mulm gets sucked in.

How do you remove or hide Mulm?

You can remove mulm with an aquarium siphon. Low flow areas are where detritus can build up and accumulate. It can also get stuck behind aquarium decorations like driftwood and rocks. Be careful when vacuuming gravel if you have shrimp or baby fish in your tank. To gently remove any debris, some breeders prefer to use a turkey baster (also known as the siphon tube) or airline tubing.

This method is ideal for aquariums with fish who can swim in high currents. Increase the water flow in the fish tank using power heads or circulation pumps. By blowing the detritus into the water column, it has a greater chance of being sucked up by the aquarium filter so that the particles can be mechanically strained out of the water before returning to the fish tank. Filter clogs can be caused by too much mulm. If it is a hang-on back filter, the filter may overflow.

There are many ways to minimize the appearance of mulm in a substrate for a planted aquarium. This will ensure that your fish tank does not look dirty. Substrates that are small and tightly-packed (such as sand), tend to build up mulm faster because debris cannot get into or embed itself in the sand. Therefore, choose a mottled, tan-colored substrate so that the mulm is camouflaged and blends in with its surroundings. A second option is to choose a substrate that is small and pebble-sized (such as gravel or Seachem Eco-Complete). This will allow the mulm to sink between the particles and reach the roots of the plants.

Gravel-like substrate with a varied brown color is great at camouflaging and incorporating mulm particles.

You can find more tips and tricks to keep your aquarium looking beautiful and clean in our other maintenance articles: