Please Help. Losing Fish

[lee.tonya]

I have a 46 gallon bowfront tank. I lost my external filter and biowheel that operated my undergravel filter system. I replaced it with an Aqueon 75 internal filter and removed the undergravel system. I did a 50% water change and used a piece of my old filter and added it to the new filter. Since the new filter has been in place, I have had fungus attack several fish. I have been doing 25% water changes every other day. My water parameters read as follow: GH: 150 KH: 100 PH: 7.2 Nitrites: 0 Ammonia: 0 Nitrates: 10. I was recommended by the LFS to add Melafix and Pimafix to tank and add 1 tablespoon Aquarium salt per ten gallons. I have since raised my temp from 78 to 82. In this tank I have, 7 juvenile guppies, 1 juvenile sailfin molly, 1 juvenile dalmation molly, 2 Angelfish, 2 juvenile bala sharks, 2 bleeding heart tetras, 2 juvenile albino corycats, 1 male Pineapple Swordtail. I don't know what's going on but I don't want to lose any more fish.

 

[Catfishlover]

Maybe try to put the undergravel system back? I've never had a problem like this.

 

[Chad]

Losing a filter a pretty big shock to a tank. That removes the biological filtration that keeps the ammonia and nitrite at bay. It's going to take a while to build back up again. 

 

[lee.tonya]

I can't put the undergravel system back in as I already got rid of it. My ammonia and nitrite levels have been at 0 since I put the new filter in. My nitrate level is at 10 , so I do not believe this is the reason for the deaths of my poor fish. I just lost another fish within the hour. I did add an extra airstone, is it possible they are getting too much oxygen?

 

[betta fish]

What test kit are you using to test? it does sound like your tank is now going through a cycle after changing the filter and undergravel plate, it is not possible that your fish are getting too much oxygen especially from air stones, so I would not see this as a cause.

 

[Meeresstille]

I'm by no means an expert in filtration, but as I read your post a second time I'm wondering if your substrate may be at fault? You said, you had an under-gravel-filter, this does bring the water flow from the water column down into the substrate to the filter, and from there back to the water in the tank. 
 
Now that you changed the filtration, the water is taken from the water column up into the filter, back into the tank. The flow of the water is stirring up particles from the substrate into the water column, and possibly your substrate may be full of things that have previously been filtered out, but now are making your fish sick?
 
Like I said, I don't know if that is the case, am just wondering out loud, is all! ??? 

 

[Chad]

...is it possible they are getting too much oxygen?

No. Really I feel comfortable that the change in filtration is the cause. Tests are often inaccurate and not designed to detect point values. 

 

[lee.tonya]

What test kit are you using to test? it does sound like your tank is now going through a cycle after changing the filter and undergravel plate, it is not possible that your fish are getting too much oxygen especially from air stones, so I would not see this as a cause.

I am using the API MASTER LIQUID TEST.
 

I'm by no means an expert in filtration, but as I read your post a second time I'm wondering if your substrate may be at fault? You said, you had an under-gravel-filter, this does bring the water flow from the water column down into the substrate to the filter, and from there back to the water in the tank. 
 
Now that you changed the filtration, the water is taken from the water column up into the filter, back into the tank. The flow of the water is stirring up particles from the substrate into the water column, and possibly your substrate may be full of things that have previously been filtered out, but now are making your fish sick?
 
Like I said, I don't know if that is the case, am just wondering out loud, is all! ??? 

I vacuum the substrate daily. When I changed systems, I cleaned substrate and tank while empty. This seems to be affecting only my live-bearers so far.
I haven't lost anymore fish today but I still have 3 very sick fish. I'm hoping and praying they will pull through. I am already heartbroken that I have lost 3 already within a day.

 

[lee.tonya]

Well I just did a visual check on my water babies. They all seem to be doing a little bit better tonight. Please pray or keep your fingers crossed that it will all be uphill from here and they will make a 100% recovery. I will keep you posted and thank you all for such rapid responses as I was in total panic mode.

 

[DoubleDutch]

I agree with the others. This fungus-attack probably is ammoniaburning causing damage to the (slime)coat of the fish.

 

[lee.tonya]

This guy has taken a turn for the worse. Can someone please tell me what he has. He started out with white fungus on his dorsal fin. It now has pin holes throughout his dorsal fin and the base of his tail the scales look raised like they are coming off and part of his sword is missing. He is in a quarantine box so I know he is not being bullied. I don't know if he will make it as he looks like he's in rough shape.