fish are dying....help

Question
Hi Lindsay,
Just another thought.  A week or so ago we started feeding the fish a treat of Wardley's Shrimp Pellets Formula, could that have been tainted with something that made the fish sick?  It made a terrible messy blob on the bottom of the tank, so I have not fed it to them in a few days and don't intend to feed it to them again.

When adding the salt and raising the temp, we found another dead fish.  That makes four in three days.  Don't know if this means anything, but when my daughter petted her fish "goodby", it's scales were coming off.  What ever is trapsing through my tank is taking it's toll incredibly fast.  I have five platys left and one, the male, is faultering.  Here's hoping the salt and heat help!  Not a good day!

Thanks for all your help, you have no idea how much I appreciate your advice.  I am beginning to think that there is some disease running rampant through my tank.  If that is the case, I do not know what I will do, I guess start over.

Thanks again,
Cathi
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Followup To
Question -
Hi Lindsay,
I'll just get right to the tank stats for you.  20 gallon tank, bio-wheel 170, fluval 2plus internal filter, bubble wall, temp holds a steady 75.2 degrees.  8 platys, 2 oto cats and two cories.  We started the tank in early January, it was fully cycled and doing fine.  I use the chemical reagent test kit (test tubes) as of this morning - Ammonia 0ppm, Nitrites 0ppm, Nitrates 5ppm, I never let my nitrates go above 20, you never know when life will get in the way and you won't have time to deal with it.  The lights are left on 10-12 hours per day.  The tank is situated in a south facing room, but is not in direct sunlight.

Three weeks ago I decided to remove the gravel.  I did so over the course of three weeks in small increments.  I also kept a baseball sized amount of it in a nylon which is now resting in the corner of the tank.  I have had NO spikes in ammonia or nitrates.  I never change both filters at the same time.  I change one, rinse the other and reverse it the next water change, except with the fluval I only change the carbon insert and rinse the foam filters.  I also use a product called Nitra-zorb which I recharge and install at every cleaning.  I do a cleaning and water change about every 5-6 days.

During the past five days or so, we have had a bloom of some kind.  There is what I am assuming is brown algae all over my fake plants and my water is cloudy, but what is worse, my fish are dying off one by one (two in the past two days and one on the way out).  Last night I increased the aeration by bringing the fluval internal filter to the surface of the tank and adding the aeration nozzle to the output.  My line of thinking was that the algae may be eating up to much oxygen.  Today, we have another fish that seems to be on the way out.  She's laying on her side etc., the water seems to be less cloudy than yesterday, but I did a water change anyway and added one tablespoon of aquarium salt (I have read that cories do not tolerate salt well, so I am stepping on the side of caution, please let me know if I have been mis-informed!).  I also gave the affected fish a short salt bath, it may do nothing to help the fish, but at least I know I tried.  She is now in our breeding box and is still alive, just not well.

What is up with my tank?  I've kicked off the lights, I've read it can stress fish even more when already stressed.  All my fish are hiding, but they are NOT clamping their fins.  Should I take a wait and see approach or what?  I know my water parameters are correct as I had a test kit on standby since the other is almost gone and have tested the tank using both kits (paranoia is setting in!).

Please let me know if there is anything else I can do or should do!  I think I have done all I can, but you never know.  Just so you know, I am opposed to dumping a bunch of chemicals in my tank unless absolutely neccessary!  Not to mention, I wouldn't know what to use anyhow!  LOL!  I am new to this hobby and enjoy it immensely, but my line of thinking is that most chemicals aren't that good for people so how can they be good for my fish?

Thank you for any advice you can give me!  I am starting to get very nervous!!!

Cathi
Answer -
Hi Cathi,

It sounds like you are doinge everything right for your tank!  I'm sorry your fish aren't doing too well, let's see what we can do to help them.

The brown algae can come from something in your water if you added tap water during your last water change.  A lot of times phosphates are to blame, but they are easy to take care of.  If you would like to try eliminating them to see if that will help your fish (I know it'll kill the algae!), you can go to a fish store (not PetCo or PetsMart, they usually don't carry them) and buy a phosphate pad.  It's a sponge-like pad that you cut to fit your filter and use in place of it for a while until the phosphate die out.  I have had nothing but good experiences with these, and they're not too expensive.

Leaving the light off is a good idea, you're right, it can stress the fish a bit more.  I would suggest raising the temperature to around 80, though, because with the lights off the temperature can sometimes lower, and warmer temperatures help fish heal faster.  The aquarium salt was also a good idea, just in case, although I've never heard anything about corys not tolerating salt.  I would believe they wouldn't tolerate sea salt, as in a brackish tank, but a teaspoon of aquarium salt to every five gallons of water is not going to raise your salinity over 1.002 or 1.003, so no worries.  The salt bath you did probably didn't do anything unless you saw ich or other external parasites on the fish.

Without being able to observe your fish myself, there's really little I can tell you to do other than, as you said, "wait and see."  The aquarium salt and warmer temperatures are great, I wouldn't go with any chemicals until you see something on the fish.  There's a chance you may have an internal parasite or possibly gill flukes or something, but it's best not to treat something that's not there, and that wouldn't explain your cloudy water.  And when you say it's cloudy, is it white cloudy?  Yellow?  Brown?  Green?  The fact that your ammonia tested at 0 is what's tripping me up.

The only thing I can think of that is out of the ordinary is the deal with the gravel.  What made you decide to take it out?  Why are you only keeping a bit of it in the tank?  I'm sure you know that gravel helps break down harmful bacteria and stores beneficial bacteria, just like a biological filter; unless you're going to be replacing it with sand or another substrate, I can't see a reason to remove it.

Please get back to me with a little more information if you can.  I've put a call in to a friend and fellow hobbyist, I should be hearing back from him in a few hours.  I would like to have more information on your gravel situation and what the fish look like, what visible symptoms they have.  Look closely at the gills, do you see anything coming out of them?  Are they gasping for air?  Are they floating, sinking, or swimming normally?  Are they twitching or swimming erratically?

I hope I can be of help to you, I look forward to hearing back!

-Lindsay

Answer
Cathi,

The shrimp pellets only made a sludgy mess in your tank because they went too long without being eaten.  Only feed those at night, and only a few because corys are generally nocturnal.  In the morning if you see any sludgy bits left over, take those out.  You don't want uneaten food in your tank, especially without gravel! :)

If your fish's scales were coming off when she petted it goodbye, that's normal, don't worry about it.  I don't think you have any monster disease to worry about, I think, as I said earlier, it's just recycling.

Good luck, I hope everybody gets feeling better!

-Lindsay