Spread Of Disease Among Fish.

fatheadminnow · Feb 23, 2009

This is not happening in my tank. Just thought I would say that so no one gets worried...lol.

I am just trying to learn a few things here, so feel free to post whatever.

Lets say some fish in your aquarium have Ick, and you did not know it, and you decided to add a couple more fish to your tank. What is the likely hood of the disease spreading to the new fish? Also, if the older fish have other diseases as well?

What I am trying to ask is, how vulnerable are fish to diseases that are already present in the tank?
Also, do medications kill of beneficial bacteria?

Thanks
-FHM

RushingChamp28 · Feb 24, 2009

fatheadminnow said:
What I am trying to ask is, how vulnerable are fish to diseases that are already present in the tank?

The fish you add to the tank are generally more succeptible to diseases already present in the tank. A large number of factors encompassed by the term "water quality" can affect the fish and stress it more during the adjustment period to the new tank. This stress is the ideal opportunity for disease to take hold (not just ick, all diseases really).

Some factors:
pH
Temperature
Dissolved oxygen content
Nitrogenous waste - nitrate, [ammonia, nitrite] <--- hope not!
Flow rate
Photoperiod, light strength
Other nutrient concentrations
Cover/habitat
Tank inhabitants/behavior
Existing stress in [store] tank

There are many factors that the fish, being living organisms, need to adjust to. Those are just a few, probably the biggest being pH and temperature, as these are the ones most commonly measured and the ones everyone is advised to look into, although there are many more contributing factors to the "happiness" and health of a fish other than those listed above.

fatheadminnow said:
Also, do medications kill of beneficial bacteria?

Yes, some medications can inhibit growth of or kill off Nitrosomonas and Nitrobacter (filter bacteria), while some are relatively harmless. Make sure you read all medicines carefully before using them. If you have questions about specific meds you can most certainly find the answers here in these forums.

Hope that answers your question
-EB

Colin_T · Feb 24, 2009

Most fish diseases will affect all the tank's inhabitants, including any new fish that are added while the disease is still present in the tank.

Whitespot (Ich) is a protozoan parasite and will definitely spread to any new fish in the tank. It will also affect every fish that has been in the tank for a while. However, some fish are more resilient and have less problems with Ich and this allows them to live with small numbers of the parasite on their body, and not succumb to it.
Other protozoan parasites that spread rapidly from fish to fish include: costia, chilodonella, trichodina, and brooklynella (in saltwater).

Some bacterial infections can spread from fish to fish but the main one to watch out for is Columnaris (mouth fungus). Even tho it is called mouth fungus it is actually a bacterial infection and a real nasty one that spreads rapidly and will kill within days.
Another bacterial infection that spreads from fish to fish is Tuberculosis (TB). This is a very slow growing bacterium that is hard to diagnose and impossible to treat. Often you don't even know the fish has it and you occasionally lose one to the disease.
Most other bacterial infections only affect the individual fish. If a fish gets injured then a bacterial infection can get into the wound and cause problems. Fungus can also get into the wound.
Internal bacterial infections are often spread to other fish when a sick or dead fish is eaten by its tank mates. The other fish pick up the bacteria with bits of the body and ingest it. Thus becoming contaminated.

Fungal infections generally only affect an open wound on a fish. They won't spread to other fish unless the other fish are also injured and have unhealed areas or sores on their body or fins.

Internal parasitic worms can infect all the fish in the tank. Some types of worm can spread directly from fish to fish. These are usually the threadworms or round worms and some produce live young that float around the water column until they get ingested. Then they set up home in the fish's intestine.
Tapeworms and other worm eggs usually need to be ingested before they can infect a fish. They have several stages to their life cycle and one stage usually encompasses living in a crustacean or mollusc (daphnia, copepod or snail). The fish eats the infected organism and this allows the worm larvae a chance to develop further (usually into an adult) inside the fish.