Dead fishies

Question
It's me again!! bad news one of mickey mouse platies, the male died yesterday. i am not exactly sure why, i wanted to ask u if fish just die sometimes and there is nothing that we can do about it. but this morning i noticed my other mickey mouse platy has this weird thing goingon with her skin. it looks like her skin is flaking. i think i even saw pieces of it floating around in the tank, but i am not too sure. but i know her skin is flaking it's not al over like spiky, it's more like flaking like wen u clean fish to eat and you use a fork to flake them. i am worried about my fish. i am also worried about my filter, the area where the water flows back into the tank has  accumulated this brown stuff. it looks like algae but brown. the water makes it look hairy, from what i can tell it isn't spilling over into the tank it's just kind of sitting there. i am worried about it though, what is my best solution forgetting rid of it. what do i do about my platy and how often do u change your filter cartridge? my boyfriend told me to just run it under hot water and it will be fine, he says they can last awhile, but i have 8 fish in a 25 gallon tank or a 30 can't remember(not includingthe babies) and i think i need to change the cartridge. it looks relatiively clean but i dont know what it's suppose to look like dirty. please help me. i dont wantall my fish to die. one last question is there anything i can add to the tank regularly to help prevent common fish disease? thanks for your help, i am very sad i feel like so much is going wrong, please help!        diana

Answer
Hi Diana
I'm going to answer both of your questions here on this one just to make it easier.

First, no you cannot catch ich from the fish or the tank.  As far as I know, the only "disease" you can catch or what is considered zoonotic is fish TB.  And, it's not the same TB that us humans get, but if you have an open sore on your arm or hand, and you have some fish infected with fish TB, there is a possibility for it to be transmitted.  I've seen photos where it wasn't too bad of a case, and one woman that had it really bad.  Now, fish TB is actually pretty rare, so I wouldn't stress a whole lot over it.  If you have open sores, dont' put your hands in the tank, wait till they heal.  Wash your hands/arms after you do have your hands in the tank. They do make special long aqua gloves as well that protect your hands/arms when working in the fish tank:

http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=3871

Ich looks like grains of salt on the fish.  It's about the same size as that, and just looks like someone sprinkled salt on the fish.  It usually starts out on the fins/tail, then spreads to the body of the fish.  Fish will also usually scratch or maybe dart around the tank as well, kind of like they're trying to itch or rub the parasites off of them.  
The fish swimming around all weird like....that's not a good sign.  My first thought is some kind of poisoning.  Did you recently do a water change?  If so, did you use a dechlorinator?  One time I was cleaning something in tap water, and put it back in the tank, and one of my platies started going nuts like that swimming around all jerky.  I added some dechlorinator then, and he stopped.  So, that small amount of chlorine/chloramines in the drops of water were enough to affect the fish.  
I don't recall how long your tank has been set up(and I apologize, but it's not easy to go back and search/look for old questions/answers, it's a long list not in any particular order)If you haven't done a water change, what's the ammonia and nitrite levels reading?  The fish could be stressed out and irritated if there are ammonia and nitrites present.
Another thing along those lines, is your ph staying stable?  If the ph fluctuates too much, that will stress/irritate the fish and can cause them to act like that as well.

And, it could be a sign of parasites.  Darting around, scratching, rubbing on objects, etc. could also point to parasites, but they do point to water quality issues as well, so I suggest checking out the water quality first-because it's easier to treat/correct.

I don't want to advise treating for ich at this point, without knowing for sure if that's what it is.  Let me know if you can get a photo, I can take a look at it.  And one thing when treating ich, it's one of the few problems where you're actually treating the tank, not the fish, so it's a good idea to just let the fish stay in the tank.  Here's a few links with info on ich as well:

http://en.wikipedia.org/wiki/Ichthyophthirius

http://www.peteducation.com/article.cfm?cls=16&cat=1791&articleid=2421

http://www.aquahobby.com/articles/e_ich2.php

The scales flaking off....another one that's hard to pin down exactly, usually caused by stress-from poor water quality or overcrowding, fish being picked on, or possibly from parasites.  Again, I would go the route of checking your water quality, make sure the ammonia and nitrites are at 0 ppm, nitrates under 20 ppm, and the ph is staying stable-and hopefully in the 6.0-8.0 range.  Think you said you only had platies in the tank as well correct?  If that's the case, you can go ahead and add some aquarium salt at 1 tablespoon per 5 US gallons, it won't hurt, and if it is a parasite infection, it may help as well.  Just remember that salt doesn't evaporate, it's only removed through water changes, so if you remove 5 gallons of water, replace 1 tablespoon of salt.  Be sure to dissolve it first in some water before adding to the tank.
If you have any salt sensitive fish-loaches, catfish, plecos, tetras, skip the salt for now.

How often are you doing water changes now?  And how much water are you changing each time?

The brown stuff in the filter, it's harmless.  Just a mix of beneficial bacteria and algae etc.  I have it in my filters as well.  I only clean it off every so often when I clean out my filters(which is rarely lol, maybe twice a year).  Don't be obsessed with having a pristine clean tank.  The yucky dirty stuff, is usually good and beneficial in some way or another.  
For the filter pads, if you rinse them off in a bucket of used tank water when you do your water changes, just scrub the gunk off with your hand, usually once a month is good, then you shouldn't have to replace them but every 3 months or so.  The directions on the packages will say to change them anywhere from 2 weeks to once a month, but that's just the manufacturers trying to get more money.  So, save your money, clean them once a month(again make sure it's a bucket of used tank water), and reuse them for at least 3 months.
I don't use those filter pads though, I just buy a bag of filter floss for a few dollars, and stuff a big wad into the filters.  I also leave a little bit from the old one when I change them out, to help the bacteria colonize in the new hunk.  Much cheaper all around.  

Back to the platies, yes they can die from an "apparant" no reason death.  But, usually there is a reason, we just don't see it or figure it out.  Most community fish like platies and such have about a 2-3 year life span-some will go longer, and obviously some a lot less.  Plus, in my opinion, they tend to be overbred and inbred, so they aren't as hardy anymore.  I rarely have a livebearer live longer then a year.  I did have a platy that lived to about 4 years old once, and have one now pushing about 3 years, but on average, they go within 6 months to a year for me.  And other livebearers-guppies, mollies, etc. even less....But usually they can have internal problems and show no major symptoms of it, until it's too late, or not at all.  

As for a prevention, I don't recommend anything be added to the tank.  That just leads to immunity issues, similar to what us people are dealing with antibiotics and such.  Weekly water changes of at least 25%, don't overstock the tank, don't overfeed, feed a varied diet, quarantine all new fish for at least 2 weeks in a separate tank-and possibly even automatically treating for bacterial and parasite infections as well in the QT tank, those are really the best suggestions for keeping a healthy tank.  

Good luck and let me know if you have more questions.

Christy