the trend is like this:
bitcoin up: altcoins down
bitcoin down: altcoins down.
and this is mostly true for most of the altcoins. and specific to the top altcoins with bigger market caps.
you will always find exceptions. it will be most common in small coins. when they have a pump coming for them for example. but you can not make a rule out of it. one rally they may rise with bitcoin the next they may get dumped even harder than the rest.
the rule that i have found to be working best is to be extra careful with ALL the altcoins when bitcoin is on the move big time. this means watching for the signs of a dump like walls disappearing, a big sell being initiated,...
Was for months on poloniex trading (exchange) from february to july every day. They show all cryptos on one site. So I saw, as Bitcoin went down, most of cryptos also did (was good visible because they went from green to red). Of course there where exceptions, but the majority followed the bitcoin trend. Best example is ETH. As Bitcoin went up from 2900$ to almost 5000$ ETH went from 50$ to over 300$.
Ok, at the moment alts could br down because we have a special situation right now with Bitcoin, so people are buying it because of hardfork.
