Is it possible for someone to lose money while following profitable alt coin signals if bitcoin goes down?
The reason why you will lose money when the price of bitcoin go down is because of the relationship between the price of bitcoin in the entire crypto currency market. Bitcoin occupies a significant percentage to the extent that, when there is an increase in the price of bitcoin, it is expected that other altcoins will have to follow the same pattern the same thing applies when there is a drop in price and because most alts cannot go be converted to fiat directly without going through btc.
What's best way to prevent it?
On avoiding it, you need to focus on alt coins that the price movement in relation to the prices of btc is not as sharp as others in that a general market increase might affect it but a downward does not necessarily means its going down or the effect would be fatal. Again, you need to do away with those signals and to do that, you need to ask yourself what is the gain of that individual giving the signal and what is the cost to those who will be ripped off which eventually might get to you.