The useless junk they try to sell you

What about the stick-on thermometers stuck outside the tank? I find these influence room temperature thus leading to false readings.
 
I don't think this is classified as useless junk, but I think its close.

Most of the advice of Big Box stores: I'm not saying that all of the advice is wrong, there are some people in the pet trade industry who actually know about this kind of stuff, but some people aren't as informed as others. They'll try to convice you to buy a certain product even though you don't really need it. Or in a worst-case scenario, they'll try to convince you that a certain fish will only grow to a certain size or will grow to the size of your tank.

The cure for this is research on the internet. Always research on the internet from at least 4-5 websites with information about the kind of fish you want. Don't buy a fish just because it looks cute or on impulse. Do your homework first. :)
 
It can, but table salt does just as well, hence the myth element - that table salt contains toxins which will harm the fish.

Regular table salt is in fact not good for fish as it contains too much iodine. Kosher salt is pure salt with no additives at all. If you need salt, use Kosher salt. Safest way to go. I keep it on hand anyhow for my margaritas (that I can no longer drink). I also use it on Bluefish and Striper before I freeze it.

Some so-called aquarium salt is actually Kosher salt in a fancy package.
 
Ammonia-removal products.

While they may have a purpose during certain emergency-type scenario's, they fall in the category as 'junk' when promoted to be used full-time or on a routine basis (beneficial bacteria performs the same job for free).
 
The Artificial Decorations: Castles, No Fishing signs, Sunken Ships, and houses to name a few. Fish would like it better if you spend that money on a nice piece of driftwood, some artificial rock formations or plants more than a fake boat. Do you find these decorations at the bottom of the Amazon river or in natural pools in Southeast Asia?

not just sunken ships, just sunken ships with real fabric sails! real fabric that ends up ROTTING in your tank because it's not meant to be kept underwater. figure that one out. . . . .
 
Feeder goldfish, the worst food for anything. They're malnourished, disease-ridden, and often have been doused with 'color-enhancers'. Poor little things.
 
I don't find anything wrong with stick-on backgrounds.. sure, theyre functionally useless, but i find them aesthetically pleasing, and not detrimental.
 
Regular table salt is in fact not good for fish as it contains too much iodine. Kosher salt is pure salt with no additives at all. If you need salt, use Kosher salt. Safest way to go. I keep it on hand anyhow for my margaritas (that I can no longer drink). I also use it on Bluefish and Striper before I freeze it.

Some so-called aquarium salt is actually Kosher salt in a fancy package.
Several of us have long used table salt on fish as per treatment with no ill results. Since when did the table salt have "too much iodine" for human consumption? This is only a myth. Iodine cannot kill a fish. Excess iodine has symptoms similar to those of iodine deficiency. Commonly encountered symptoms are abnormal growth of the thyroid gland and disorders in functioning and growth of the organism as a whole. Elemental iodine, I2, is a deadly poison if taken in larger amounts; if 2-3 grams of it is consumed, it is fatal to humans. Iodides are similar in toxicity to bromides. If the table salt has "too much iodine", then it is not suitable for human consumption nor is it for fish. If table salt is not suitable for fish, humans would have met the same ill effects as the fish did.

Again, table salt is fine for use. Aquarium salt is only packed in fancy packages as part of their marketing ploy. Most petstores want nothing but profit whether their actions are ethical or unethical.
 
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