Some say the ich protozoan is ever present in most tanks & ponds & only becomes problematic with poor water quality & stressed fish. Do you think this is true?
No, that is rubbish. White spot and velvet have to be introduced into an aquarium. They can do this on fish, plants or in contaminated water or objects. You might only get one individual parasite/ pathogen in the water and it can take weeks or even months to build up in numbers. Sometimes if the tank is cleaned regularly (with big water changes and gravel cleans), the disease organisms never get a chance to build up in sufficient numbers to infect the fish on a large scale and show symptoms. Then you can have a low grade infection in the tank that doesn't really affect the fish and never shows itself except for an occasional flash/ rub on an object in the tank. And fish can and do get the odd itch so most people don't think anything of it if it only happens once. Most people also don't watch their fish 24/7 so a fish can rub on objects when people aren't around.
I had a tank with a group of young rainbowfish in. The tank had been established for years, had plants and got regular maintenance. It had never had white spot in it before. The water was perfect and the fish weren't stressed, but they were dying slowly one every few days. I couldn't see any diseases and they weren't showing symptoms. I took one to Fish Health at the Department of Agriculture. They necropsied the fish and said it had white spot and gill flukes. I treated the fish with salt and copper and got rid of the white spot and flukes. But none of those fish were stressed or showed spots on their bodies. They had the problem for months and it was kept in check because I was doing huge water changes and gravel cleans, which diluted the number of parasites in the water. It turned out the fish came from over east and the supplier had apparently treated them for white spot before sending them over to WA. They obviously still had a parasite on them when shipped and it built up in numbers in my tank and started killing the fish.
If fish are stressed, they are usually stressed by poor water quality, a dirty tank or filter, or from being bullied or kept in unnatural numbers or in the wrong water chemistry. These will all weaken a fish's immune system and allow disease organisms easier access to the fish, and the dirty conditions will encourage harmful pathogens to build up in numbers. This is one of the reasons I tell people to do a huge water change and gravel clean every week, to dilute disease organisms in the tank.
Diseases caused by stress and poor water quality are usually external protozoan parasites like Costia, Chilodonella & Trichodina. These diseases are in most aquariums but don't normally cause problems unless the tank is dirty, doesn't get regular cleaning, and is overstocked or heavily fed (especially with meat foods).
Poor water quality (in particular water with ammonia in) can damage the tissue of fish and allow harmful bacteria and fungus into the wound. This can then spread and if left untreated, can kill the fish. Virtually all aquariums do have harmful and beneficial bacteria and fungus in them. It's introduced with the fish, plants and anything else you buy or get from an aquarium. A lot of bacteria also floats around in the air and can land in aquariums where it settles down and grows. A lot of harmful bacteria, fungus and protozoa can live in biofilm (the slime on the inside of the glass, ornaments & filter in the aquarium). If you wipe the glass down every week or two, and wipe or hose off ornaments regularly (at least once a month), you remove or reduce the biofilm and minimise the number of harmful pathogens in the aquarium.
There are some harmful bacteria that can only get into your aquarium via a sick fish or contaminated water. The most common one is Columnaris (aka mouth fungus). It's actually a flesh eating bacteria but starts out as a white mouth, hence the common name mouth fungus. I have never had this disease in my home tanks but we saw it in the shop regularly. It came in on sick fish (usually guppies) from the suppliers, who sent out sick fish when they shouldn't have. If you catch the disease in time, you can stop it with salt and medication (usually antibiotics or antibacterial medications like Formaldehyde and Methylene Blue). Neon Disease is another one that has to be introduced.
Stress does play a big role in fish health, but has nothing to do with white spot or velvet. You can have really healthy fish get white spot, and you can have fish in poor water quality and they don't get white spot. It has to be introduced into the aquarium.
---------------------
I did not calculate water volume. All my tanks were sold as 55, 75, 90, 110, 125 gallons etc & I trust the manufacturers to get it right. The IchX instructions were 5 ml per 10 g.
Don't trust the manufacturers. 99% of aquariums don't hold as much water as what they are sold as. Some tanks might hold that amount if they are completely full to the brim, and when there is no gravel or ornaments in it, but most tanks hold less water than what they are sold as.
Gravel, rocks, driftwood, plants and even fish displace water. Most aquariums are filled to a couple of inches below the top. These all reduce the amount of water in the aquarium. External filters can add water volume to an aquarium.
You should always work out how much water is in a tank before treating.
When measuring large aquariums to work out water volume, you should measure from the inside of the glass because 1/2 inch thick glass can add an inch to the total length, width or height and add a few more incorrect gallons of water to a tank.
Try working out the volume on one of the tanks and see how close it is to the manufacturer's claims.
Andy, most of the pics at that link were banned or X’d out.
)
