Fish dying. Please help.

[Jedi Kaleo]

I am new to the hobby and have scoured a good chunk of the aquarium co-op videos but I am stumped. I have a 20 gallon long, plants, driftwood (has clear fungus, but was told this was not harmful) gravel, few store bought decor, and a sponge filter. I started with about 10 neon tetras,  1 rubber lip pleco, 1 hill stream loach, and 1 nerite snail a little over 4 weeks ago. Immediately a handful of the tetras died off. I did not thinking anything about it and assumed shock or bad brood from the store. The pleco died after a week, it never did seem to eat and only hid. Over the course of the following weeks a couple more tetras died. I started noticing what looked like ripped fins. I assumed fin rot as there is no observed aggression, and since I did not quarantine I went ahead and treated the tank with melafix, paracleanse, and super Ike. I just finished the regiment and another tetra died, and the fins on the last two look more torn with white tips starting. On top of that the snail has been staying a the top of the tank out of the water since just before I started treatment which sounded like water quality but perimeters have been consistent and tested daily with API master kit. 

ph: 7.2-7.6, ammonia, nitrite and nitrate: 0, kh: 54 (3 dkh), gh: 160 (9 dgh)

Please advise as I have no clue how to proceed at this point. Thanks in advance. 

[Colu]

As you have no nitrates your tank more than likely hasn't cycled and you could be getting swings in your pH nitrites and ammonia  did   you cycle the tank before adding the fish did you add  all the fish at the same time had you resently done a water change before they died if so did you use a water dechlorinator like prime and what's the temperature of your tank

Edited May 19, 2022 by Colu

[Jedi Kaleo]

The aquarium appeared to cycle before I added the fish. I used Fritz fish less fuel and Fritz 7 (bacteria) to boost the cycle. Ammonia and nitrites went up and back down, and I had assumed the plants were keeping the nitrates down. The fish were added at the same time. I have been using api stress coat conditioner and have made 25-40% water changes once a week, typically after I noticed a fish struggling or one died.  I have not had any spikes when testing water daily. Water temp is 78 steady. 

[Guppysnail]

I’m sorry you are off to a bit of a rocky start.  Getting started is rough.  Do you have an airstone or sponge filter running? Have you run a test for dissolved oxygen saturation?  The snail staying above the waterline may be a lack of dissolved oxygen issue. That will in turn stress your fish, stress lowers the effective functioning of their immune system. This is just a possible guess as I don’t know your tank/fish personally.  
edit I just reread and you do have a sponge. I would still test as new tanks are heavy with water column bacteria that consumes lots of oxygen and medication lowers dissolved oxygen. 

Edited May 19, 2022 by Guppysnail

[Hannah Parker]

Did you use all those medicines at the same time? That can be taxing on the fish and might've be hard on them. I also know a lot of fishkeepers that say neons are sickly and hard to keep in general. I'm glad you posted and asked the forum for help, there are a lot of knowledgeable people on here and I'm sure they can help you get to the bottom of it. 

Edited May 19, 2022 by hannah662parker

[Jedi Kaleo]

Yes, I ran the medicine regiments in tandem (I believed this to be the appropriate direction for “new fish” quarantine per some of the articles unless I was mistaken). I ran a second air stone through the treatments but I will look into how to test for oxygen. Thanks for the tip. 

[Guppysnail]

This is the one I use. It could also be the paracleanse or Melafix irritating it.

[Colu]

Adding all the fish at once it possible beneficial bacteria wasn't able to multiple quickly enough to keep up and adding the three medication at the same time could have caused the desolved oxygen levels to drop causing some of your fish deaths  even with an extra air stone as melafix is oil based it can lower your levels of desolved oxygen quite a bit 

[Chick-In-Of-TheSea]

Nerites go above the water line all the time. It's part of their normal behavior.

I don't think the issue is air since you said you added a second airstone.

Do you have a heater?  When you do your water changes (with water conditioner to dechlorinate), are you making sure the water you add to the tank is the same temperature as your tank water?  (I use an instant read meat thermometer to check the tank temp, then I also use it at the faucet when filling my bucket).  Fish do not tolerate temperature fluctuations very well.

When you first bought your fish, did you float the bag in the tank to help them adjust to temp?  (Another way to do it is through drip acclimation)

Edited May 19, 2022 by Chick-In-Of-TheSea

[Torrey]

On 5/18/2022 at 10:32 PM, Jedi Kaleo said:

I started with about 10 neon tetras,  1 rubber lip pleco, 1 hill stream loach, and 1 nerite snail a little over 4 weeks ago

That is a lot of fish to put into a new system at one time. 

There's a good chance this is one part of a larger problem. 

On 5/18/2022 at 10:32 PM, Jedi Kaleo said:

On top of that the snail has been staying a the top of the tank out of the water since just before I started treatment which sounded like water quality but perimeters have been consistent and tested daily with API master kit. 

ph: 7.2-7.6, ammonia, nitrite and nitrate: 0, kh: 54 (3 dkh), gh: 160 (9 dgh)

Please advise as I have no

KH is a bit low to provide the necessary stability long term. 

You say ammonia, nitrite and nitrate are all 0 ppm, and you are using API liquid reagents (test tubes).

Are you running activated charcoal and purigen?

If not, are you shaking the liquid reagents before holding the reagent bottles perfectly perpendicular to the ground, to count the number of drops going in?

The reagents for pH are a little more forgiving. 

The reagents for ammonia and nitrites require more precision to get accurate results. 

Nitrates will give you a false 0 ppm reading unless you shake both bottles of reagents well, and shake the second bottle of reagent and the test tube until you are pretty sure your arm is going to fall off.

At a pH of 8, ammonia and nitrite are extremely toxic.

The snail is communicating that something is wrong. 

Plants, especially riparian with roots in the water, are the fastest way to give your fish a buffer while doing regular water changes to keep ammonia & nitrites as close to zero as possible, and give the tank a chance to properly cycle. 

[Jedi Kaleo]

To Chick-in-of-thesea: yes to all of your questions. 
 

To Torrey: no to the charcoal or purgien. Yes, I am following the liquid tests instructions to the letter and backing it up with test strips periodically. I even took a sample to the local store to have it tested to make sure I was reading them correctly. I have never had spikes in the aquarium after it cycled and then added the fish. 
 

As an update the Loach died over night. Nothing seemed wrong (no spots, parasites, fin rot,etc.) other than it hide a lot except at night which I assumed normal, and it did not seem to eat the wafers, repashy, or zucchini that I put in (removed/replaced after 24-48 hours). It did however eat some algae off the driftwood and glass. I’m waiting on the O2 test to come in tomorrow as no local store had that, but will probably pulling the snail and last two tetras out tonight just to be safe. I was reading that excess algae could lead to low O2 (maybe?). Little bit frustrated with myself on this today. Thanks for y’all’s help.