Swordtail breathing on the top of the tank?

Question
QUESTION: Hey, David. Haha, my name is David,too. I have a question about swordtails. I have a 20 gallon tank. 4 swordtails, 2 zebra danio, 3 tetras and 5 shrimps. My 3 of the smaller swordtails are swimming on the top of the tank just now, and then its breathing air out of water. Other fishes seems don't have the problem of finding hard to breath. I did some research about bad quality water. I found the reason might be high ammonia? I don't have a test kit for ammonia yet. So I cant give you NH ppm. I wonder whats happening to the swordtails. pH is fine. Temperature is fine too. I changed 25% of water today. I removed chlorine too. I just wash my sponge filter too. Here is the activity that I did to the tank. In the afternoon, I went out to buy a driftwood and some plants. I washed them with tap water before I put them in. It was fine until now which is 8 hours after. Can you help me with this problem? Thank you.

ANSWER: Hi David... did you clean your gravel today when you changed your water?  If not you should.  Ammonia builds up in the gravel.  Driftwood will lower you pH also in the long run but it is possible that the driftwood "tainted" the water so that some of the fish are feeling the effects.  You can take a water sample to the local aquarium and have them test if for you... most do this free of charge.  Warmer tank water will carry less oxygen then cooler water... so if the tank warmed up it may have lost oxygen.... not sure if this helps... but a full chemical analysis of your water would make it easier....  keep me posted... dave

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QUESTION: Hey, dave. I cleaned the gravel like a week ago. I did a 75% water change and vacuumed the gravel. Today i went out to buy ammonia test kit and I tested the water. The result was pretty good its below 1.2mg/L. I think its around 0.6. My pH was fine all the time. It is right now 6.8. The temperature is 75 degree F. Then I decided to stop using the filter for a while and connected the air pump to a air stone. The fish seems to relax now. Do I really need a air stone? then I guess I have to buy another air pump. But my sponge filter is making bubbles too? Maybe not enough? How do you clean the gravel when shrimps are around? Do I have to take them out first?  Thank you for helping!
-David

ANSWER: Hi David:  Ammonia should be close to zero.... You did a good job cleaning the tank but try not to remove more then 20% of the water or your tank will start to cycle again.  Taking too much water out will deplete the good bacteria.  I would add a second air pump and a stone... just get a small one... cause the sponge filter is doing some oxygenation too.  Shrimp!  just gravel vacuum really carefully when dealing with a tank that has crustaceans in it.  Hope this helps... dave

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QUESTION: Hey Dave, my fishes are doing fine now. They are eating well and swimming well. A week ago, I noticed some of my fish had red gill. It's not that red, so I didn't check online. Today I went online to check what caused red gill. I found out that it is because of ammonia, but my ammonia level is zero now. Can you tell me more detail about red gill. If you can, show me a picture of red gill. I want to make sure that I am looking at the right thing.

Answer
Hi David:  I don't have a picture of gills to share... but gills should be red... just not inflamed.  red gills are healthy and its where the red blood cells pick up the oxygen, etc.  Keep your eye on the fish and since your ammonia levels have gone down the fish should in a few days start to exhibit normal gills.  Oxygen is important too... so make sure you have an air stone.  you can look at air pumps that have two outlets... hope this helps... dave