If you are just starting to get your feet wet in terms of aquarium keeping, you probably know that you need to do weekly water changes, but you may not know everything included in weekly tank maintenance. During your water change, you should take the time to vacuum the gravel, shift decorations frequently, and clean the filter media. Cleaning the gravel is something that most new fish keepers don’t know about, despite its importance.
You do need to clean the gravel in your aquarium to prevent nitrate spikes. The gravel, while porous and very effective at building up good bacteria, can also hold a massive amount of mulm, which is damaging the long term. Some types of gravel are very small and are not porous, which can lead to anaerobic conditions developing if it is left alone for too long. The good news is that these threats are very easy to mitigate and don’t take any extra time during your weekly water change.
In this article, we will discuss why you should clean aquarium gravel, gravel siphons, how to clean gravel without disrupting your cycle, cleaning sand and bare bottom tanks, cleaning rocks and other decorations, and cleaning algae on gravel.
Why you Should Clean Aquarium Gravel
The primary reason you should clean your gravel is to get rid of any mulm buildup between the rocks. A buildup of mulm will happen in any tank, whether it is from fish waste, plant material, or leftover food. If this is left in the gravel for too long, it will begin to cause nitrate problems and could even lead to anaerobic conditions.
Nitrates are the final stage of the nitrogen cycle in aquariums, and while they are the least harmful, buildups can easily push them to dangerous levels. In a clean tank, weekly water changes are easy to keep nitrates low. However, if you do not properly clean the filter media and vacuum the gravel, nitrates will quickly build up, no matter how well you stick to your weekly water change schedule.
Anaerobic conditions, while relatively rare, can have lethal consequences. Most gravel is porous, which allows water and other material to easily flow through the gravel. This is ideal for growing good bacteria, allowing some mulm to fall between and stay away from your fish, and for keeping up a cleanly appearance. However, if the pores become clogged with material, water will not be able to flow as well, and some areas may be deprived of any water flow.
Without water flowing through bringing dissolved oxygen, anaerobic conditions can start to appear. If the areas without oxygen also have a buildup of mulm, anaerobic bacteria will begin breaking down the mulm. Instead of just releasing normal, but toxic, ammonia, they are also capable of producing hydrogen sulfide gas, which is harmful if released into the water column. If you avoid vacuuming your gravel for a significant period of time and suddenly decide to, you run the risk of releasing the toxic gas into your aquarium.
Gravel siphons are widely available and come in many different sizes. The larger the tube, the more area you can cover, and the faster your water change will go. You should keep your eye on your fish when you use it, as some will be intrigued by all the “food” particles going up the tube, and they may try to follow it.
Some people like to match the size of their siphon to their fish, while others like to match it to the size of their tanks. You should take into consideration the size of your decorations when you buy your siphon. Be sure it can fit between various decorations and the sides of the tank so that you can clean all of the gravel.
How to Clean Gravel Without Disrupting your Cycle
As previously mentioned, some of the good bacteria that keep your aquarium cycle going live in the gravel. There are differing estimations on whether most of the bacteria live in the filter or in the gravel, and it likely changes from tank to tank.
Most people like to err on the side of caution when it comes to maintaining your cycle, as it can take more than a month to correct it. The general recommendation is to clean 1/3 or less of your gravel each week. However, a little more or a little less won’t be a bad thing.
Be sure that you are not vacuuming the exact same patch of gravel every week. Cycle between each 1/3 or so of the tank. You should be able to vacuum the whole tank every 2-3 weeks, which will prevent the buildup of any mulm.
Cleaning Sand or Bare Bottom Tanks
Cleaning sand bottomed tanks is a bit trickier while cleaning bare bottom tanks is incredibly easy. Unlike gravel, if you plunge the gravel vacuum into the sand, you’ll end up removing all of your substrate. Luckily, most of the mulm will rest on top of the sand.
To remove it, gently swirl the gravel siphon above the sand, paying extra attention to any visible areas of mulm. The swirling motion will lift the mulm right into the tube. It is recommended to have some type of fish or invertebrate that will churn sand. This will lift extra mulm to the top and prevent anaerobic conditions from forming. Aquarists commonly use Malaysian trumpet snails and Corydoras catfish for this.
If you do not have any tank inhabitants that can churn sand, you should take a knife, fork, chopstick, etc. and stir the sand a bit yourself every week to release any trapped mulm.
Bare bottom tanks have no substrate, so you simply need to gravel vacuum anywhere you see visible mulm. Bare bottom tanks are not common, as aquarium keepers normally use them only for extremely messy and large fish.
How to Clean Rocks and Other Decorations
Another essential part of weekly tank maintenance is cleaning your decorations. Unless you have an algae problem, you likely won’t have to clean the actual decorations. However, you will need to move them, as mulm frequently gets trapped under decorations. This, in turn, can cause a nitrate spike if not taken care of.
If you do see a lot of algae or visible grime on the decorations, they are easy to clean. You will need a bucket of old tank water if you need to put them back into the tank immediately. However, you could also rinse them under tap water and dry the decorations before returning them to the tank.
Take a new toothbrush or similar and scrub the grime off of decorations, while periodically rinsing it in water. It typically only takes a few minutes to get a decoration looking like new.
Algae on Gravel
Removing algae from gravel is a bit trickier than cleaning mulm out of gravel. Algae is caused by an imbalance of nutrients, carbon dioxide, and light. This means that even if you clean your gravel of algae, it will continue to come back unless you fixed the conditions that caused it.
It takes some time to figure out which aspect caused the algae (unless your tank gets direct sunlight from a window, as that will always cause algae), but if you really need your tank to look clean in the meantime, there are ways to temporarily remove it.
Remove all the gravel from your aquarium and put it in a mix of water and bleach. Be sure the bleach is pure and doesn’t include any scents. This will quickly kill the algae, but before you put the gravel back in your tank, you will need to get rid of the chlorine.
Rinse the gravel several times in tap water, then submerge it in water again. Add in extra dechlorinator and let it sit for a day or more. Between the dechlorinator and the chlorine naturally off-gassing, the bleach will dissipate from the gravel.
In conclusion, you need to vacuum gravel to prevent a buildup of mulm, or organic material. This buildup becomes very harmful long term and will make tank maintenance nearly impossible if not dealt with. Gravel vacuums are easy to use and make tank maintenance and weekly water changes easier and faster.