Sick Mollies and Rainbow fish

[BlueFish2112]

Hi. I am a fairly new aquarium owner, and I am looking for some advice.

1. I have a 75 gallon tank that has been set up since Nov 25, 2015. (photo attached)
2. In my tank I have:
-5 rainbowfish (2M, 3F) (added 30-Jan-2016)
-1 redtail shark (F) (added Dec 2015)
-1 opaline gourami (F) (added Dec 2015)
-2 platies (1M, 1F) (added Nov 2015)
-3 Mollies (1M, 2F) (added Nov 2015 & Jan 2016)
-3 Kuhli loaches (added Jan 2016)
-I also have ~10 baby platies from a previous fish that I am planning to put up for adoption later today.
3. My tank has an undergravel filter with powerheads along with a quiet flow filtration system that is mounted on the side of the tank.
4. My tank parameters have been pretty stable.
-ammonia 0ppm
-nitrites 0ppm
-nitrates 0-5ppm
-pH 8.2
-temp 80 degrees F
5. I last vacuumed the gravel out on 31-Jan-2016 and I last did a 25% water change 6-Feb-2016. I normally change ~40% of the water every other week, but since I've had some sick fish, I've been doing this every weekend.
6. I feed them all Omega One fish flakes, Tetra Pro Tropical Color Crisps, freeze dried bloodworms, and some zucchini that I dehydrated (I re-hydrate before feeding). I feed them every other day and switch which food I use, only using 1 type of food a day. I also have TetraMin tropical tablets for my bottom feeders.

At the beginning of January, I had a silver Molly (not listed above) die. She would sink to the bottom of the tank and couldn't get to the surface. I scooped her up in a net and held her closer to the surface to try and help her get some more oxygen. She died later that day. About a week later, my black lyretail Molly had the same behavior. She normally wasn't an active fish, so I might not have caught the symptoms in time. I didn't realize anything was wrong until she was lying on the bottom of the tank and was dead by the next day. I bought both of these Mollies from the same tank at the pet store at the same time around the beginning of December. My ammonia, nitrite, nitrate, pH, temp had not changed throughout this time. Nothing looked physically wrong with the fish. They just unexpectedly died. I thought maybe I just bought some old fish since they were on the larger side.

After my 2 female Mollies died, my third Molly (M) started to mope in the corner of the tank. He is my favorite fish, because he was normally very active and let's be honest rather adorable. I thought he was sad because his lady companions disappeared. I bought two more female mollies mid-January. The male Molly seemed to perk up a little bit, but still hid in the corners from time to time.

I recently went to a new aquarium store where I bought my rainbow fish and loaches listed above (30-Jan-2016), and the guy running the store told me that my fish would be happier if the pH of my tank was closer to 7. I don't really have access to RO water, and I don't have the means to buy jugs of water from the store. I did buy some Seachem Neutral Regulator from the store to try. On 31-Jan-2016, I cleaned the tank, did a 50% water change, and I added about 4 oz of the Neutral Regulator before I realized that my water was too hard for this to be a feasible method. I couldn't get the pH below 7.8. It was back to 8.2 by the next day. At the same time I did this, I also added a large piece of driftwood to the tank. I realize now that it was not properly cleaned/sterilized before adding it to the tank. It was just rinsed off really well before adding it. 20-20 hindsight...

Since then my male Molly really started to get worse. He always hid in the corner and ran away whenever a baby platy approached his general area. (I attached a photo of him hiding.) He had brief moments where he was swimming around as happy as before, and then he was lying on the bottom of the tank. He was fluttering his fins without really going anywhere. He physically doesn't look any different than he did when I got him. I took him out and put him in a little 2.5 gallon tank with a heater, airstone, and a little plastic plant. I started treating him with Marineland all-in-one-remedy. He has had 3 treatments so far. He's just starting to swim around again but is still spending a lot of time on the bottom of the tank. He still has an appetite, so I'm hoping this treatment is working.

Now, I just noticed that one of my rainbow fish has sequestered herself in the corner my Male Molly had been hiding in. I read that is bad when school fish isolate themselves. She has a stringy poop on her. I tried to get a pic of it. Most of the time the fish don't have poop hanging off of them, and before when I saw it, I wasn't worried because I thought it was from the zucchini I was feeding them. But it has reappeared and I have fed zucchini in a while.

I'm getting a little frustrated with my fish dying off one after another. Does anyone have any thoughts on identifying what is actually wrong or how I can resolve this issue?

Thank you!

 

[Matt68005]

Have you observed any red paintbrush like threads coming from the vent?
It sounds like camallanus worms, or some other nematode.
Most often they come from the petstore this way. Do not ever buy a flat bellied or bloated fish, especially livebearers as they are prone to camallanus.
I am not sure this is the case, but it is what it sounds like to me.
It is not easy to get rid of and sometimes breaking the tank down and stearilizing everything is the only way to completely get rid of this parastiic worm.
Levimasole can be effective in the early stages, and prophalatically when getting new fish. You can buy it in flake form online from angelsplus.com, or you could just buy some powder or liquid from ebay or amazon. But i believe it has been discontinued, so may be hard to find.
It probably came from a sick molly, and may be next to impossible to get rid of. I would take the tank down, euthanize the fish and bleach everything scrubbing all corners and all heaters, toss the filter pad and substrate, and start over.
Like i said they do make de wormers, and ofc it may not even be worms, but it sure looks like the early stages of it. In the early stages they get stringy poo, then the stop passing feces all together, finally you see the worms prodruding from the vent or even moving inside the fish's intestines. Once you get to this point, the fish cannot pass the worms even if you treat them, and the worms rot inside the host fish and kills it.

 

[BlueFish2112]

Hi. Thank you for your response.
I have not seen any red on the vents of any of my fish. The rainbow fish that was isolating herself has rejoined her school, but she still has the stringy poop.

Also, I would just like to clarify. When you say euthanize the fish, do you mean just the ones that are sick? Or are you saying that they all are potentially infected?

 

[Matt68005]

Im saying that they are all probably infected and that there could "possibly" be worm larvae all over your gravel which will never go away.
Keep a close eye on their.....vent over the next few days/weeks..... if another one dies, cut it open in the stomach and observe. If it is red worms in their belly, you mine as well take it down and clean everything because they will never go away 100%........

 

[BlueFish2112]

I will keep an eye on them. Thank you for your advice.

 

[BlueFish2112]

Hi. As an update, my male Molly died. He did not have any red around his vent. I opened him up too, but I didn't see any worms inside.

 

[Matt68005]

You wont really see them until the later stages, but it is wierd he died so soon from it.
These internal things are tough....