The Aquarium Water Care Guide

Taking care of a large (75 gallon or more) fish tank may seem like a daunting task, but the basic steps are the same as a smaller tank. Some steps, such as maintaining ideal chemical levels, can actually be easier with a large tank – the added water volume can be more forgiving.

Here are the basic steps required to maintain your fish tank. Follow these to keep your fish happy and healthy.

Water Changes

Perhaps the single most important thing you can do to keep your fish healthy (besides remembering to feed them!) is performing regular water changes. These don’t entail draining all of the water – rather, portions of the water are drained and replaced on a regular basis.

This is an essential step to keeping harmful chemicals at a minimum. Left unchecked, substances such as ammonia and nitrate will build up in the water. By draining off a portion of it on a regular basis, you constantly dilute the water with fresh, uncontaminated fluid, avoiding this problem.

On a weekly basis, drain at least 10% to 15% of the total water, and replace it with fresh water. Tap is fine, just make sure to first remove any chlorine with a treatment chemical. Once a month, your flush should be more intense – roughly 25% to 30% of the total water volume.

These flushes are vital, so make sure to keep track of them.


A clean home is a happy home. Cleaning is usually done at the same time as a water change. You’ll want to vacuum the gravel at the bottom of the fish tank, as random particles (such as uneaten food) can settle in the substrate and contaminate the water over time.

During these cleanings, you may also wish to clean algae buildup from the sides of the tank. This will help provide a clear view and keep algae contamination to a minimum. While cleaning, also take the time to check the filter, which is necessary to ensure the water remains clear between water changes. Replace the filter’s carbon when necessary.

Chemical Checks

You should keep a variety of aquarium test strips on hand to keep up on various levels. Water pH, softness, and ammonia and nitrogen levels should all be checked routinely. Although these will usually stabilize after the fish have been in the tank for some time, it’s a good idea to check these at least once per month. If adjustments are required, use the appropriate additive to remedy the problem (low pH, for example, would be corrected with a pH+ chemical).

Read more here: How to lower pH in Fish Tank.

Fish Tank Maintenance Schedule

Here’s a sample to use as a cheat sheet. Follow these steps (based on the more detailed instructions listed above) at the recommended intervals for an easy schedule to keep your aquarium thriving.

On a Daily Basis

  • Ensure the pump is active and circulating water
  • Check the water temperature to ensure it is within recommended levels
  • Make sure the lights are all on

On a Weekly Basis

  • Take a headcount of your fish. If any have passed away, remove them from the tank
  • Perform a 10% to 15% water change
  • Vacuum the gravel and clean the sides of the tank
  • Check the filters
  • Make sure the electrical cords are securely plugged in and show no signs of damage

On a Monthly Basis

  • Check the tank for any small cracks or leaks. Catching these early can prevent a bigger problem down the road.
  • Perform a 25% to 30% water change
  • Use your test strips to ensure there aren’t any drastic chemical fluctuations
  • Replace carbon in the filter(s)
  • Check all lighting bulbs and clean the cover to ensure adequate light output
  • Check tubing to make sure it’s intact

In addition to this regular schedule, it’s a good idea to do an annual checkup on issues that don’t necessitate monthly maintenance.  Check the expiration dates on foods, chemicals, and testing products, and immediately throw out anything that has expired. This is also a good time to disassemble the water pump, clean the impeller, and oil if necessary. All pumps are different, so check your manual to see if there are any specific instructions in regard to pump maintenance.

All of this may seem like a lot of work, but most of these tasks take very little time and can help avoid major problems down the road.


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