Welcome to Aquatic Warehouse!

Top 4 Reasons New Fish Die in a Tank

Why New Fish Die in Aquariums San Diego, CA

Even though aquarium fish are traditionally kept for their ornamental value, we tend to appreciate them as pets. For this reason, seeing these aquatic creatures suddenly dying can be extremely frustrating. Quite a few tropical fish don’t have long life spans, but even guppies should live a couple of years in a healthy ecosystem. Some of the tiny saltwater goby species will only live about a year in captivity or in a natural reef habitat. Since the fish you get from aquarium shops are usually juvenile, you should expect to keep them for about three quarters of their regular life span. If they die shortly after you introduce them to the tank, one or more of the following issues may be to blame.

1. New Tank Syndrome

A newly established freshwater tank is expected to have gone through most of the nitrogen cycle, which includes the formation of Nitrobacter colonies and thus eliminating potential ammonia. You still need to stimulate another round of bacterial bloom before the cycle comes to full completion, and this is provided by the fish you stock the tank with. New tank syndrome is what happens when nitrite levels peak higher and faster than the bacteria can handle, thus resulting in an interruption of the nitrogen cycle. In addition to testing the water before stocking the tank with fish, you may want to start out with just a few hardy species to allow bacteria to thoroughly colonize.

2. Too Many Fish

Going beyond the one inch of fish per gallon of water is a recipe for aquarium disaster. Overcrowded tanks have a higher bioload that seasoned fish keepers strive to avoid. Ammonia levels are at the heart of the tank overstocking problem because too many fish will always result in too much fish waste, and you may not be able to handle it with frequent water changes alone. Always remember, more filtration will be a benefit in that it will make up for mistakes in feeding and crowding in the future when your fish grow.

3. Unsuitable Aquarium Conditions

Before introducing a new species to a tank, it’s good idea to conduct proper research on the kind of habitat conditions it requires. Let’s say you keep a freshwater aquarium without a heater (Note: it’s always recommended to install a heater even in the summer and set it to 78 degrees F so your fish will be protected from stress on the nights that drop below that temperature). Should you introduce an angelfish when outside temperatures drop, it may not survive too long. Similarly, if you introduce a Plecostomus in a tank without plants, you’ll have to make sure its herbivorous nutritional needs are being met with the right kind of fish food.

4. Native Parasites

In saltwater and reef tanks, surgeonfish often host parasite microorganisms such as Cryptocaryon irritans. They may not be affected by these parasites, but they can certainly pass them onto new fish that aren’t as resilient. It’s important for aquarists to keep a close eye on fish that are newly introduced to tanks because they may be coming from ecosystems with different conditions. It’s best to feed garlic (aquarium garlic without the oils in it), as this will expel parasites systemically. It’s super cheap with super results.

Caring for your aquarium properly is the best way to ensure your fish live long and healthy lives. You can find all of the freshwater and saltwater aquarium supplies you need at Aquatic Warehouse, located in Kearny Mesa. You can also order whatever you need from our website and have it shipped to you. If you have any questions, don’t hesitate to call us today at 858-467-9297.


Contact Information

  • Address: 5466 Complex Street Suite 204
    San Diego, CA 92123
  • Phone: (858) 467-9297
  • Email: sales@aquaticwarehouse.com
  • Working Days/Hours: Mon - Fri / 10:00 AM - 7:00 PM
    Saturday / 10:00 AM - 6:00 PM
    Sunday / 11:00 AM - 6:00 PM


Site Security

secured by

SSL site seal - click to verify

Google Reviews