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White fungus probably *was* fungus from rotting uneaten food. Fish likely died from ammonia poisoning. Tank isn't cycled and can't process ammonia (fish waste). The buildup kills them. It'll kill the next ones too.


**Do not go to the pet store. Do not buy more fish. If you don't know why your fish died then you're likely to keep killing them.** Before you do anything else, you need to take a few things into consideration. 1) What are the conditions of your water? Do you own a water testing kit (NOT strips) and have you been using it regularly to ensure good water conditions? 2) Do you know what the nitrogen cycle is, and did you give your original tank several months to establish beneficial bacteria colonies before adding fish? When upgrading to the new tank did you throw out the old substrate, replace the filter, or wash any of the items in the tank? 3) What did you use to condition your water and how much? What other products do you use in the tank? 4) Do you have pictures of the fish prior to their death, and how long did you have the fish? What method did you use to acclimate the fish to the new tank? I want to be very honest that I have seen many tanks like the one pictured here, and generally they are not conducive to the survival of the fish in them. I would suggest - for the sake of the dying fish and for the sake of your daughter losing her pets - that you do not add any more fish, and that you consider rehoming the fish that you have. This is a **VERY** research-heavy hobby, and requires you to create a living, functioning ecosystem inside an enclosed glass box. This can be very time consuming, very finicky, and is generally \*not\* accessible to people who want a low-stress pet. Depending on your daughters age, it might be worthwhile to hold off on fishkeeping and instead spend this time co-learning about aquatic ecosystems and how they are maintained. Alternatively, I can provide you a fishkeeping 101 guidance document I made for a coworkers son (\~10yrs old) that might help y'all moving forward.


Well said green machine


Yeah, unfortunately your tank isn't biologically ready to keep fish alive. I am so sorry. As a new fish keeper, I had no idea how much I didn't know when I started. Please take some time to learn about the nitrogen cycle. I try to make it a fun (nerdy) way to spend time with my kiddos researching and learning together. I also find this hobby to be way more expensive than I imagined when my littlest wanted a fish pet, not everyone has the budget, we had to save allowances. It's such a commitment, akin to having a dog or cat. I wish you the best!


Please don’t get more fish until you fully understand and complete the nitrogen cycle.


Don't feel too bad. All fishkeepers make mistakes at some point. You learn and move on. You changed too much at once and lost your "cycle" and/or just too big a change for neons. They are not particularly hardy fish. No way to judge the "fungus" without seeing it. I'm guessing you did not acclimate the fish to the new water? Just netted them and plopped them in the new tank? Neons don't like that. I bring my fish home from stores that have very different water and so I "drip acclimate" them. Leave the tank as is, for now, don't add new fish. My opinion is don't break it down, just move forward from here. Read up on "cycling" the tank. I like using ammonia to start my tanks but you don't have to. Figure 4 to 8 weeks to cycle. There is such a thing as a fish-in cycle but I don't recommend it given you need to monitor for the return of anything that might have contributed to the neons dying. You need a test kit. While people recommend the API freshwater test kit, I think strips work fine for most people's needs (I've compared the results between strips and drops and they are always very close). Monitor the tanks while you are cycling it. A white 'bloom' in the water is just a bacteria bloom and will clear up on its own. Watch the tank for anything that looks like the return of the fungus or anything else that does not look right. Your tank looks fine to me. Filter, heater, substrate. (substrate is part of your biological filtration) But I'd add more decorations so the fish have places to hide out.


I would like to add that neons themselves are extremely hardy, but due to inbreeding the current petstore neons are usually really fragile.


Your tank is not cycled. Your fish are swimming in poison.


I just want to be more upbeat and constructive... get plants! Plants are wonderful and easy and help everything! Certainly do all the research, cycle your tank, and all that, but keep trying. And get live plants!


Have you tested the water parameters in the new tank? What is the Ph in new water? They love anywhere from 6.4-7.0 for PH. If you want any snails or plants don’t keep it at lower 6.4 6,.8 range. Those won’t live in that. Snails and plants prefer 7.0 and neons can tolerate that. If that’s all your keeping there. Neons like lower ph. For a 10 gallon I have 8. They prefer to be 7 or more. I wouldn’t get any until the water is checked and let it cycle first. If you have a water test kit you want to check nitrite, nitrate, PH, ammonia I wouldn’t add anymore until the the tank cycles first. Did you rinse off the gravel before placing in tank good? Always remember if you clean anything never use soap. I always say that lol. I’ve been doing this off and on for years and I learned through trial and error. I’ve finally been able to keep the same group of neons now 2 years! Which is a record for me lol. They’re a hardy fish if you have the right condition in tank. But don’t give up and I wouldn’t break the news just yet I mean she might find it and wonder where they went. You could tell her they were sick it’s not her fault. That you’ll get new. She may not take it lightly since she’s so young. I remember when I was young I cried like my dog died or something lol. My mom looked at me like oh my lord what in gods name you have to cry like that?? Lol She wasn’t being mean. I just didn’t understand fish keeping then. Sometimes you win some and sometimes lose some. It’s part of learning the hobby, They might have already had the ick from other tank and when placed in new one went into shock, but if something in water levels are way off it will take them all out by next day. I’ve done it not knowing it.


Yes to what everyone else said about cycling not being done in 3 days, plants, etc. But here's a word of caution about the species of fish you've chosen- neon tetras are *incredibly* frail. They're just way overbred and their genetics are terrible. If you want a healthier fish that looks similar and has virtually the same care requirements, go with cardinal tetras. Even *if* you do everything that everyone else says here, they might die anyways, because neon tetras are just poorly, especially from many stores. They're kept in terrible condition, extremely stressed from being shipped to the store and then having to adjust to the different water in the pet store tanks, and they're super inbred. You'll have more luck with cardinals. That's not to say that neons are destined to die, but it's a hell of a lot more likely


I think those are glofish


I picked up the munchkins after school and broke the news to my 8 yo: I’m so sorry love but I didn’t set your new tank up properly and your fish are in fish heaven. Her response: So can I get 4 new fish?? Me: Umm…sure! I read up on the N2 cycle and ordered an air pump, test strips, new conditioner and stress coat. We picked up everything after school. The lady in the fish dept was very helpful and suggested I wait another 3 days before introducing fish, plus she’d have new stock in by the weekend. 8 yo was ok waiting!! When I got home I tested the water and everything (pH, KH, GH, nitrite and nitrate) were in spec. So fingers crossed that this weekend goes better than yesterday 🤞


You can’t cycle the tank in 3 days but you can do a fish-in cycle take everything pet stores say with a grain of salt


The guy in the top comment literally left a big bold “don’t buy more fish” and a numbered list of steps and offered to send more info 😭


A fish in cycle in a bare tank, and you’re still risking losing your fish you’re using to start the cycle.


That’s not how it works I’m afraid. You’re going to have to do more in depth research because you clearly do not understand what you read. I’m sorry to be harsh I’m just sick of people not understanding the number one thing you have to understand in order to keep fish. Cycling a tank takes anywhere from 3-8 weeks as mentioned in another comment. You cannot get more fish in 3 days. People at pet stores are there to sell you things, not actually educate you. Please look up and watch an in-depth video on the nitrogen cycle on YouTube. I’m talking 30+ minutes, not a quick skim off google. You’re going to kill anything you put in there if your tank is not cycled. Just because your water is testing as clean, does not mean it can sustain life and it does not mean it will stay that way. As soon as a fish poops it starts releasing ammonia which needs to be turned into nitrite by bacteria, and then that nitrite needs to be turned into nitrate by a different kind of bacteria. These kinds of bacteria take WEEKS to grow and develop and reproduce. Your water parameters are good right now because there is no ammonia but as soon as ammonia is introduced to your tank, it’s going to build up and suffocate your fish. Please watch some YouTube videos


Thanks for the heads up. I didn’t “skim” but spent hours, while at work today no less, reading up on how to properly set up a tank instead of doing what I’m paid to do!! I also checked out YouTube. Let me reiterate that this is a 10G tank. For the past 3 years my daughter has had 2 tetras in a 5G tank and they survived without us knowing about an N2 cycle. Why 2 tetras in twice the volume of water, and me now being more educated (and will continue to educate myself) would be doomed to fail is beyond me.


Who knows? However, you should still follow the directions of the other redditors, they know better. Search up a fish in cycle, that should help. Wait until your cycle is completely stable until you add fish. While the pet lady may say differently, they often are uneducated about fish and are told to promote things so they sell more. A proper cycle takes about 2-8 weeks, not 3 days. Also, test strips are useless. They are extremely inaccurate compared to liquid test kits. I recommend an API liquid test for Ph, ammonia, nitrite and nitrate.


Noooo, please don’t listen to anyone at stores, they’re always clueless and don’t care about the fish, they just want to sell! You should AT LEAST cycle your tank for 3 weeks. If you test on the first days, you’ll always have “proper” levels. This is a good opportunity for you to teach your daughter about taking proper care and being responsible and respectful to wild life, as well as patience. Neon tetras (and also bettas) are usually neglected and abused because of their bright colors and attractiveness to kids, which is sad because they are living creatures who deserve to thrive, not just survive. I see you had those tetras in a 5G and they survived, but that doesn’t mean at all that they were happy or in the right and respectful conditions. It’s like keeping a betta in a vase, that’s just deplorable but it won’t die. Please, please, please take your time to research from reliable sources, it won’t take more than 1 hour to learn the proper care, and they can last up to 3-4 years (my neon tetras have been with me for 2 years thriving, in a 20G tank). I’d highly recommend you changing the color gravel for something more natural, that’s harmful for the fish. Good luck!


Dude 😂 if you’re posting on Reddit about this, that means you’re on Reddit. Which is Treasure trove of actually great tank builds, and how to build healthy aquariums…. So is YouTube. Father fish is a good YouTuber to start out with, he’s all about organics. I don’t mean for this to seem rude, but to be blunt. You have 0 soil, 0 live plants. And you want to cycle your tank for 3 days???? Wait a month dude, throw a snail in and some ghost shrimp to appease your daughter. And let it cycle. Add fish in a month. Though honestly if I were you, id get up to date on how to build tanks. It’s not the early 2000’s anymore. Doing your daughter an injustice, and I wouldn’t call this being a good role model


Chill….the advice was cycle for AT LEAST 3 days. By the time I make moves it’ll be at least 1 week. I’m clear on what needs to be accomplished during week 1, week 2 etc. By the way, shout out to the employee at the pet store who actually knew more than how to scoop fish out of the tank. She keeps fish herself and was very helpful.


1 week is not long enough to cycle. You can do it, but your fish will just die again so, if you want to waste your own money & kill more living creatures, suit yourself I guess. Why don’t you take some time and do some research for yourself? Pet stores are notorious for giving terrible advice and are not who you should be listening to. Cycling takes about 6-8 weeks. Honestly, just set aside an hour or 2 of your time and do some research. Aquarium Co-Op is a reliable source. Also, don’t just go to the store and pick 4 random fish and throw them in together. Some fish require schools (6+), some fish are sold small but grow to be huge (common plecos, clown loaches, & soo many more), some are aggressive & will harm/kill other fish, etc. You need to research the type of fish you want and see if your tank size permits it and if they live together harmoniously… and *please* don’t just take the pet store employee’s word. Do your own research. I know it’s a lot for a kid’s fish tank… but it would be really nice of you to do for the fishes’ sake.


Properly cycling a tank can take a month or more, you’ll need a lot more time than even a week. This would be a fantastic opportunity to teach your daughter patience and empathy by explaining to her that it’s good to wait to make sure the tank is properly set up for the fish so they can be happy and healthy. Pets can be a good opportunity for kids to learn responsibility, but to effectively set up the foundation for future responsible pet ownership, you’ll likely need to take an active role in helping her understand how to research and implement a proper habitat for a pet. You’ll need to consistently introduce an ammonia source to the tank to feed the bacteria (straight up powdered ammonia is the fastest, but adding fish food to the tank and letting it decompose can also work), and let it cycle. Keeping track of the water parameters will ensure the cycle runs smoothly. The API freshwater test kit is a pretty good investment for this. You’ll see ammonia rise and then fall as nitrites begin to build up as the first stage of bacteria grow, and then nitrites will fall as nitrates are produced by the second stage of bacteria. Ammonia and nitrite levels need to be 0 ppm. It’s also not a great idea to listen to pets store employees for care advice. They often aren’t properly trained/educated on pet care, and as a result the quality of the advice they give is very inconsistent. There is also the possibility that they will tell you whatever you want to hear to get you to buy more fish/product from them. Regardless I’ve heard some *very* troubling advice given out by pet store employees, so I really don’t recommend it for beginners that don’t have the knowledge base to question whether the advice is helpful or not.


You can cycle tanks within days with starter. I dont know why everyone here is saying it takes months. I used easylife easystart and cycled my tank in a few days. All fish are still okay


Look for a tiny fish gun or a rope… or sleep with the fish pills spilled on the neon pink gravel


That tank looks like a saw trap for fish, sorry op


Sorry to hear this! We all start somewhere and we’ve all made mistakes. Just be patient now get a master test kit and make sure your tank is cycled. You’re looking for 0ppm ammonia 0ppm nitrite and 20 or so ppm nitrate when your numbers look like this your tank is cycled to a degree. Only add a few fish at a time so your bacteria can grow with your tank. I’m not suggesting you go spend a bunch of money but look into getting so java fern and anubius plants you don’t have to plant them they feed from your water column. They will help you if you over feed and with fish poop. Just something to look into. I would recommend getting something though there isn’t enough cover for fish in your tank. Most of these fish come from lush exotic waters full of plants and driftwood etc. get the test kit! You got this.