Black molly & soft water

I wouldn't. I try to buy the type of fish that prefer the water I've got. They have a greater chance of living their entire lifespan and with fewer diseases. Most South American fish like softer water. Mine is perfect for cichlids. I'd love to have softer water. Not sure what you mean about the ick question.

Kim

Contrary to popular myth, Mollies are not usually a brakish water fish. They don't need salt to live happily. As far as their ability to eat hair algea, My understanding is the young fish will eat it, but the adults don't do so as readily, so they aren't the best choice as an algea eater.

As far as ICH, I'm not sure what the question was, but anytime you introduce a new fish without quarantine, there is a chance of introducing ICH into your tank. ICH can go undetected on the gills of otherwise healthy fish, and then someday when a fish is stressed or weak, it will break out.

One of my "friends" gave me some plants (java moss) that had a hidden hair algae in it. I didn't want to bleach it first and now my tank is infected with this ugly algae that I never had.

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Hair algea can and will show up without a formal introduction, so I wouldn't be too hard on your friend. Any algea outbreak is an indication of something being out of balance in the tank, What are your water parrameters, what do you dose as far as ferts? What other plants do you have etc. more information will make it easier to help you.
Algea eating fish can help keep a tank clean, but as a rule in any tank that has major algea, the fish alone won't take care of it, the cause will need to be found and changed.

I was linking this to another reply and thought you might be intersted as well, Here is an article that specifically addresses moolies and salt.
The great molly debate
dave

This link is a great resource for mollies. I will usually post this link when this question appears or if mollies need salt question appears.
Mollies are found in a far range of waters, from soft to hard, salt to fresh.
Most store bought mollies though can live in fresh water but prefer the water to be hard.
jim

My tank was perfectly balanced until now. I still don't have an outbreak, but it annoys me. Thanks!

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If you don't have a real outbreak, I'd reccomend a lot of trimming, one of the things I've found with J moss is that it doesn't take very much at all to grow out into huge bunches. I'd trim aggressively everything that you can see hair algea on, and whatever is left will expand quickly in a well balanced tank. I throw away about a pound of J moss every 2 weeks or so (and my tank has yet to become well balanced), and am forever pulling it off of areas where I don't want it to grow and removing it from my other plants and filter sponges. It is a great plant in the respect that it is hard to kill and will grow anywhere. I started with1 very small ball (would have fit in a tablespoon) and 3 months later, I have it in three differnt tanks in large healthy quantities.
dave