Those are the guidelines of the product, "treat every 48hours"
Ok, but I think that that is wrong. Ich medications that need to be constantly re-dosed work by oxidizing cells. The hope is that oxidizing the tissues of the ich organism in its free-swimming stage (the only stage it is vulnerable to medications) will kill off the much simpler organism than oxidizing some cells of the complex organism like a fish.
The trouble is that oxidizing is a pretty quick reaction -- especially in an oxygen-rich environment like a fish tank. We know it is oxygen rich -- fish live in it. Oxidizing medication will not be active for 48 hours. It has almost no chance of even being active after still 24 hours, or even 12 hours, really.
This is why people have noticed success by performing a gravel vac before dosing ich medication. It probably isn't sucking up ich organisms as is commonly thought -- but it is sucking up all sorts of organic material that would otherwise be oxidized when it came into contact with the medication. Stuff like dead leaves, fish poo, etc. would all be oxidized if still in the tank, thusly taking away activity of the medication that would otherwise hopefully be going to kill the ich organisms.
The above is as opposed to the long-acting medications like a copper-based medicine that is designed to be stable in the tank for longer than a month.
So, knowing the reactivity of an oxidizing material coupled with the fact that some stains of ich can have a cycle as short as 2 days (especially if you turn up the temperature like many people suggest), I think that dosing every other day is insufficient.
I would strongly recommend dosing every day at the same time if possible. This way you try to catch all of the organism as it enters its free swimming stage.
Lastly, manufacturers are not always the best source of this information. There is still a major manufacturer whose dosing instructions is add once, wait 4 days and add one more time. If you understand the ich lifecycle (again, see the link in my post above) you'll see why this will never be effective.
I hate to say it, but the manufacturers are there to sell you a product. And, following inefficient dosing schedules will probably do a decent job killing a fair number of the ich organism, but won't kill 100% of the infection. And, I think that the manufacturers don't mind this. Consider the scenario: you dose inefficiently, killing 75% of the ich. The symptoms go away -- that is the fish don't show any spots and aren't flicking. So, you think you are done. Then, 10 months later, ich breaks out again. So, you go and buy more medicine. The ich breaks out again because you never killed 100%, and the fish were still asymptomatic carriers. Fish can carry the organism in their gills where you can't see the spots. And, their immune system if healthy and strong can fight off the ich for a long time.
It is scenarios like the above that lead to myths like "Ich is in every tank." Which is utter rubbish. (Not to beat a dead horse, but see the link I posted above.)
If you dose efficiently -- every day and a minimum of 7 days after symptoms show (I'd personally do 14 or even 21 days if the fish aren't showing any undue stress). You will kill 100% of the ich in your tank. And then it won't come back unless you reintroduce it by not properly quarantining new fish or plants.
So, in conclusion, I strongly recommend dosing every day, despite what the instructions day.
/www.skepticalaquarist.com/docs/health/ich.shtml It covers a lot of the facts and myths about ich. It is well worth the read, and if you have any questions, don't hesitate to post them to the forum
