JimOp

I meant Ammonia and Nitrites.

Ammonia of 1.0 is dangerously high. Ammonia and Nitrates are both very toxic.

I would continue water changes especially with ammonia levels elevated.

I would not worry too much about cause, it isn't as important as recognising an issue and fixing it. Your tank should be on the road to recovery. The water changes should have made a pretty decent dent in nitrites and nitrates by now. So please post updated water test results.

I doubt it is old tank syndrome. You seem to be well on top of your regular maintenance and water changes. You even keep a log of your water tests. Old tank syndrome is typically from lack of tank maintenance. It is a gradual lowering of water quality so slow the fish climatize to it and not affect fish in the tank, but it will kill new fish you try to add. Ignore the fish death as being part of the problem. You would see a massive ammonia spike first and it would not continue to fowl a tank after the large number of water changes you have done. Big PH swings alone can kill fish and beneficial bacteria. Acidic water can strip fish slim coats and can also burn their gills. At a basic level a cycle look sorta like this: You feed fish fish poop poop breaks down and turns into ammonia (snail poop included) one form of bacteria converts ammonia to nitrites Another form of bacteria converts nitrites to nitrates Nitrate is then converted to nitrogen gas by denitrifying bacteria, some Nitrate is used by plants. Water changes also help remove Poop, nitrate and nitrite and are important when things are not balanced Do you have an updated water test, take it a couple hours after a water change? Please provide all values even if zero. About the snails, If it where my tank I would reduce the snail count to a max 10 getting rid of as many babies as I can find. But, as you can see their are differing opinions on snails. My guess is one or a combo of both the substrate and/or aquarium rocks as being the issue. You could test some of the rocks as a previous poster suggested. Just because the stones came from an aquarium company doesn't mean they are safe.

@cr0wley About snails. Can you get a rough count as to just how many snails are actually in your tank. I would guess dozens just from glossing over the pictures. @Andy's Fish Den And more on the snails: Again, I never told them to smash them on the glass, I told them that is how I handle them in my 40 gallon breeder with fish that eat them. Summery: We are looking at a high bioload 10 gallon tank that has killed a fish. It has a PH of 6.0 high nitrites and high nitrates. They lost a single gourami. They have at least 8 neon tetras and and unknown number of zebra danios and an explosion of snails judging from the picture. On the subject of snails, how many snails are already dead from the tank PH going up and down from 6 to 7.1 to 6 every three days? You cant tell because there are possibly dozens of snails in the tank. I stand by the fact that I feel he needs to reduce the number of snails in his tank. Snails are not zero bioload, they eat crap, algae and they poop, they breath Oxygen and they die. Snails also reproduce like crazy so the act of removing a bunch of them costs nothing. The source water is listed in the Thread. They also uses fluval biostratum that they were buffering with crushed coral to get a stable PH but had removed it. The assumption is the PH drop is from having Fluval biostratum and then removing the Crushed coral from the filter. PH of 6.0 and below can kill off the beneficial bacteria. Something they kept adding with every water change and could also be the cause of the nitrite/nitrate issues. Testing the stones is a great idea, I had suggested they remove them while trouble shooting. I looked up fluval biostratum. While I have never used it, I seen references to it drastically lowering PH to 6.5 or even 6.0. Putting crushed coral back in his filter may be the solution for the PH, but I am not sure having never used fluval biostratum.

Personally I would never use copper in an all glass tank. The issue with copper is that it can get into the silicone and stay there. If you decide later to get Fresh water shrimp, it could kill them just from the trace amounts thats forever stuck in the tank. Manually removing them is the safest way to keep the ones you want. Some people suggest that dropping a piece of cucumber, zucchini, carrot, or lettuce into the aquarium overnight can get them to gather on the vegetable making it easer to remove more in one shot. I have no idea if that works or not.

And another. https://www.thedonutwhole.com/can-you-have-too-many-snails-in-a-fish-tank/

I disagree about snails not adding to the bioload especially When you are already pushing the limit in a 10 gallon tank. As far as smushing them. I have a 40 gallon tank breeder and fish that will gobble them up. I wasn't suggesting that you do that. Here is an artical about snails that you may want to read And you can make an informed decision. I am sure there are other articals out there as well. https://escargot-world.com/how-many-snails-in-a-10-gallon-tank/#:~:text=A 10-gallon tank has,for some species of snails.

Lots of suggestions on the net. here is a couple: https://www.aquariumcoop.com/blogs/aquarium/5-best-fish-tank-ideas-for-a-29-gallon-aquarium

Angels take about a year to mature but they can start breading as early as 6 months. They can live up to 10 years. They are a long term commitment. I highly suggest you start with something easier in a 29 gallon community tank. That way you can learn how to deal with tank problems before making problem tanks.

I have never used that Substrate but from what I read it shouldn't make your PH drop like a rock but it can take it into the mid 6.5 ish. Never using it perhaps the crushed coral is your PH solution. Snails you can just pick out with your fingers or use snail traps if you want, you can keep a few if you want but like I said they will constantly breed. I smush the babies in my tank and the fish eat them. but not sure if your neon's would eat them so best to remove as many babies as you can to start and keep your favorite big ones just not too many.

How long have you needed to add crushed coral to raise the PH? If you say from the beginning.. well it could be the rocks and it is worth a shot to remove them at least temporarily to see. As far as snails go it depends on the type of snails you have in there. You have 8 neon tetras that is already at the topping out the bioload that I would recommend for a 10 gallon. Add in more than a dozen snails and could be loads more babies, I can't see. Remember what I said about small changes make a big difference in a 10 gallon? You have very high nitrites and nitrates a sign the tank may be overloaded. Snails breed and keep breeding as long as there is enough food. You have PH that drops from 7.1 to 6.0 in three days meaning something in the tank is causing the water to become acidic. That's my best guesses as to what could be happening.

First major problem, WAY too many snails in the tank. I counted at least 15 from the picture. Snails poop too adding to the bioload increasing nitrites and nitrates they also breath sucking up oxygen both your plants and fish need. I would reduce snails to like 1 in a 10 gallon tank. Second issue may be the stones. Where did you get them? Some stones can leach into the water and change the chemistry. If you got them from a creek I would take them out, You may want to try removing them anyway while trying to sort out the issues with the PH.

I would like to walk back my recommendation and I agree with Lennie. As they stated you are a brand new fish keeper, I did not know that. As such caution is warranted, we want you to succeed and starting with harder fish is not the way. I agree that it is not be a good choice for someone that is just starting out. My original statement of them being chill for a cichlids is actually lost when you have no idea how cichlids act. My apologies for not realizing this was the first tank. I had not read any of your previous posts.

Let me clarify "chill" On a scale from one to ten concerning cichlids only I put Discus and Angles as 1 and 2 and Oscars and Jack Dempseys as 9 and 10.

Honestly, a 10 gallon tank filled with your source water shouldn't need coral. The water you are using is already high PH. If anything you would need a water softener with a PH of 7.8 . The fact that your PH dropped enough that you felt you needed to put coral in, tells me that what ever is causing the issue, has been in your tank for a long time. I have had aquariums for over 40 years and have never once used coral to buffer and change the PH. The other thing is that you say your doing 50% water changes every three days due to low ph is telling too. Something you have in your tank is causing these issues. Aquarium PH and alkalinity do not dramatically change on their own. Especially not as dramatically as you are seeing. That its self is dangerous for your fish. big Ph swings can kill your critters. Dead fish do not cause this kind of PH swing, Pulling the coral out would. However the coral you are adding is masking a problem with your tank. You could add coral back and stabilize the PH and be done with it, but what ever the problem is will remain in your tank. If you want to figure out why you need coral when you shouldn't, that will take a bit of trouble shooting. What you need to do is test your water and mark it down. Also I would maybe get another different brand test kit or strips as a sanity check incase something is wrong with the kit/strips you are using. Clean your filter out completely of all media, rinse it out and install the filter with out any filter media. Just using it for flow and attempting to rule out your filter media.. If your PH is in a safe range, leave the water alone. If PH is very low do a water change. Do not add anything to the water, with the exception of water conditioner if needed. Dead bacteria decomposes too and will spike nitrites/nitrates. a little high nitrates is ok with a planted tank, higher nitrites on the other hand is bad. solution to nitrate/nitrite issues is water changes. If you add bacteria to a tank with a problem and it dies, it turns into waste starts breaking down and turns into nitrites and nitrates. Test it in 15 min and test again in 2 hours. If you did the water change your tank PH should be higher. If it is still low than you need to look for something in your tank. If it is higher, Test the water the next day to see if the PH dropped. If it hasn't than there is something wrong with the filter media you are using. If PH dropped again you need to look for something still in the tank. A 10 gallon tank is a small and unforgiving environment when conditions change. Meaning that it does not take much to throw it off so changing small things can have dramatic effects to the water quality. NOTE: API Aqua Essentials should only be used to treat the water you are adding on, not the entire tank when doing water changes. Do not do a water change and then treat the tank. I use a 5 Gal Lowes bucket and treat the new water prior to putting it in the tank. Putting chlorinated water in a tank and then treating it can shock and kill bacteria, plants and fish. The water changes is what battles the PH, alkalinity, high nitrate and nitrites issues. Never use the water conditioner more than once a day. If you can post a picture of your tank. One other thing, are you using co2 in the tank?

Fix the PH issue, the bacteria will sort its self out.

Decaying plants can lower PH so yes it is possible. but if it hasn't improved since tossing it, i would keep looking. Changing out the filter media may help as there may be trapped and decaying plant matter on the filter media thats preventing the recovery until it is fully decayed, changing it is faster.

Out of all the cichlids, Angels and discus are the most chill. That being said, they all have personalities and a pair of mating angels can get aggressive, especially when mating. Adults can be as big a 6 inches so in a 29 I wouldn't put more than 4 in.

Has any thing new been introduced into the tank? Stones or decorations? Limestone can leach into your tank making the water acidic and lower the PH. Something is causing the drop. PH goes hand in hand with alkalinity. pH is hydrogen ions the acidity of water. Alkalinity is the ability of the water to neutralize or buffer changes in acidity. Baking soda is a buffer, it raises the alkalinity and that changes the PH. Essentially something is leaching acid into the water. If there is something new you are using filter media or new decorations that would be the obvious places to look. If not I would change out your filter media to see if that helps. What ever is happening is the reason you lost a fish not the result of a dead fish in your tank.

couple more questions, What is your source water look like when tested? And last are you treating the tap water? Baking soda is ok for a band aid, crushed coral is not a great solution as you may end up fighting with high ph. alkaline water and reverse your problem. Figuring out the problem and treating that is better solution.

Yeah your only real options are to swap it for a male, remove the drift wood or get something that may or may not eat them. Zebra Danios will sometimes eat the eggs but that still leaves the residue for a while anyway. Zebra's would likely be fine with a Betta but I am assuming your in a small Betta tank and the zebra danios are a fast moving schooling fish that need a bit of room. Not ideal for a small tank. Anything else that would eat them would not be good in a beta tank either.

Nerite snails need a partner to breed, and I believe they need brackish or salt water to breed in. So unless you meet those two things you should be fine leaving them. It they where sold as Nerites but actually aren't you could end up with a snail issue. However fish love escargot. I have unwanted Ramshorn snails in my tank and a school of zebra danios that do nothing but eat, crap, eat, breed, eat, did I mention eat? I smash like 11 or 12 snails a day every day against the glass and the danios gobble them up. so I call them food. those the daimios don't get either the cories or the shrimp will.

I wanted to also add that, if it was on backwards on the line, you would have no flow. That's after all the check valves purpose.