HELP-fish dying!

Question
-I have made a 25% water change

-My aquarium is 20 gallons
-been set up about 1 yr
-tank contains: 1 Dwarf Blue Guarami (2in), 1 Dwarf Chocolate Guarami (1in), 4 Banana Barbs (3 are 2in, 1 is 1in), 5 tetras (1in), 3 Albino Tiger Barbs (1in)(-1 because it died yesterday),(my Black Red Tailed Shark died yesterday also)
-Temperature 80F
-Ph 6.6 (b4 water change)
-Nitrite .25 (b4 water change)
-Ammonia 0 (b4 water change)
-Water changes are made once a month (25%). Every time I do a water change I also do a gravel vac, clean/change the filter (charcoal whisper filter), add cycle to the H2O, add aquarium salts to the H2O...I have not been as faithful changing the H2O as i should have, I pretty sure that is the source of all my problems...It has always been crystal clear
-I use Nutrifin max complete flake food (is about 3 yrs old). I feed 2-3 (at the most) a week. It takes them <5 min to eat...the rest settles at the bottom.
-What do I need to do now? Is it possible for me to save the rest of my fish?
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Followup To

Question -
Hi, I'm trying to find someone who can help me with my aquarium.  Is there a specific disease or something that affects the fish's mouth, gills, and stomach?  One of my fish can't close his mouth and is breathing really hard and is having a hard time eating because his mouth can't close!  Another fish (both albino tiger barbs) can't open his mouth very far and is breathing a little fast.  Also when the fish eat their stomachs bloat and after awhile they throw the food up.  I thought it was mouth fungus but the treatment didn't work and the other fish started showing symptoms of being sick.  I then did a water change and a couple days later I started treating with Maracyn because I thought it might be be bacterial.  I'v been treating it for 4 of 5 days now and it dosn't seem to be any better and now I have lost my black red tailed shark and 1 of my albino tiger barbs.  I'v increased circulation and oxygen hoping that would help.  Also 1 of my fish has a small white lump on the end of the top of it's mouth...If you have any information of any kind please let me know (phone number, link, site...etc.!!! Thank you so much!


Answer -
Hi Sarah;

I need a bit more info about your tank before I can help. Make a 25% water change in the tank right away and then come back to answer the following questions for me;

What size tank is it?
How long has it been set up?
How many fish?
How big are each fish?
What kind of filtration?
How often is the filter cleaned?
How often are water changes made?
How much water is replaced?
Do you vacuum the gravel?
What kind of food do you feed?
How often do you feed?
How long does it take the fish to eat all their food after you put it in? Five minutes? Ten minutes? An hour?

Let me know as soon as you can.....

At Your Service;
Chris Robbins

Answer
Hi Sarah;

The tank needs to re-stabilize from whatever went wrong. The nitrites are probably responsible for the fish deaths. Make a water change every day for the next 3 days while things get back on track. Do not vacuum the gravel or change the filters yet though. Something has happened with the biological balance. If you clean too much in the gravel and replace the filter media too often it kills or eliminates the beneficial bacteria in the gravel and in the filter. This beneficial bacteria consumes fish waste toxins such as ammonia and nitrite. You should only replace filter media when it is literally falling apart from age. I have some that have been in constant use for years. I just rinse them in tank-temperature water every so often so that they still allow water flow. It is important not to clean the filter media at the same time as a gravel vacuuming. It's just too much disturbance all at once. Do a 25% water change weekly, but not a gravel vac and filter cleaning in the same week. For instance, maybe do gravel vacuuming one week and filter cleaning the next week.

Feed the fish once a day, but only enough for them to totally consume from everywhere in the tank in 5 minutes. You don't ever want food to settle on the bottom. Fish food rots in just a few hours and can make the fish very sick if they eat it. If they don't eat it right away, the tank becomes polluted. The gravel can even become toxic from the rotting food. Yuck!

I really think the problem you are having is mostly overfeeding and perhaps too vigorous a cleaning all at once. That's why a partial water change of 25% every week and gravel vac every 2 to 4 weeks is very important. It keeps the water chemistry more stable so the system and the fish aren't stressed so much.

I hope they feel better soon.....

At Your Service;
Chris Robbins