Are you floundering when it comes to your freshwater fish tank? Fighting fish diseases or water quality issues such as ammonia is frustrating and will make your fish tank feel more like a burden than something relaxing and fun. Although a fish tank is never maintenance-free, with the proper care it should become more stable and easier to maintain as it matures. Are these 8 common aquarium mistakes holding you back from enjoying your tank?
1. Too Small Tank
Larger tanks are more stable, thus making water quality, temperature changes, and overcrowding easier to control. These are the primary causes of stress, and in turn, disease, in fish. Tanks 20 gallons or larger significantly increase success rates, although filter size, and fish size and quantities are also factors.
2. Too Small Filter
Water quality problems concerning high ammonia and/or nitrites almost always indicate insufficient biological filtration. This either means that too much waste is being put into your tank (see #3 and #4), your tank is newly set up and has not had time to get enough good bacteria to process the waste, or you are running a filter that has too little biological capacity for your set-up. A good rule when purchasing a filter is to select one rated for a minimum of 10 gallons larger than you require. A more powerful filter provides increased stability for your system. Adding extra biological media such as BioMax beads is also beneficial.
3. Too Many Fish
Overcrowding your tank can be a significant stressor for fish. Not only can the waste load become too high for the filtration system, but fish can become more aggressive as they feel starved for space. One inch of fish per gallon is the maximum recommended amount. Has your tank been set up for less than 4-6 weeks? Cut the number in half (1/2 inch of fish per gallon).
4. Too Much Food
Too much food will significantly increase your tank maintenance and can negatively impact your water quality. Your fish should be able to consume all of the food you give them within 2- 3 minutes. Food should not float to the bottom, or get sucked up by the filter. Food waste decomposes into toxic ammonia and nitrites, which lead to fish diseases and eventual death.
Be careful not to feed your fish too little, either. If fish are undernourished, their immune systems drop, making them more susceptible to disease. Feed at least once daily - preferably 2 - 3 times per day.
5. Improper Water Changes

If you aren’t doing at least occasional water changes, your water quality will eventually deteriorate, and you will have problems with disease. Changing too much water can be just as detrimental. Changing too much water, too frequently stresses fish, and thwarts tank stabilization, creating a permanently weak biological system. In this scenario, problems such as high ammonia and nitrites will never go away. You should be changing at least 20% of your water out per month (not just topping off the water), but 10-20% per week is ideal – no more.
Make use of helpful products to speed maintenance and reduce stress on your fish. AquaPlus water conditioner removes chlorine and eases fish stress by replacing your fish’ slime coating. Cycle or Stability re-energizes your ecosystem to prevent ammonia and nitrite spikes. Doubling-dosing either Cycle or Stability in tank set up or after stressful situations helps to establish biological stability.
6. Incompatible Fish
Fish who are picking on each other are always stressed, which makes them more susceptible to disease. Observe your fish during daylight hours and when you turn the lights off to monitor behaviour thoroughly. Always research species compatibility before introducing new fish to your tank.
7. Fluctuating Temperature
Temperature fluctuations are extremely stressful for tropical fish and are a common cause of disease. Make sure your heater is changing no more than 3 degrees throughout the day. Don’t put all your trust in your heater’s thermostat – have an extra thermometer or two on hand to double-check temperature.
8. Improperly Introduced Fish
Are you acclimating your fish slowly or just dumping them into the tank? When you bring a fish home, you should take at least 20 minutes to float the bag, slowly adding some of your tank water to the bag over time. This keeps your new fish from the shock of completely different water conditions that can bring on stress and disease.
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