I've lost at least 10 fish in 2 days & don't know why - any help is appreciated

This has been a weekend that makes me question why I do this. I'm saddened and frustrated because I'm not sure what happened. Today I think I'm figuring out what has happened, but I don't know what to do about it; I'd love some experienced aquarists' opinions.

About my tank:

20 gallon long, established Sept 2019
Planted
Gravel substrate
Small piece of DW
Heater preset at 78
HOB AC 30 and 2 bubblers (just removed 1 today)
KH - 6
GH - 9
PH - 7.6
Ammonia - 0
Nitrite - 0
Nitrate - <5
Phosphate .5

I use our well water which has always been fine in any tank we've had, but yes, the PH is high around here.

(I have never used a quarantine tank. Alarm Bell is ringing)

I have battled high nitrates in this tank for months and with 2 WC a week, usually 2-4 gallons at a time, and reducing feeding some, it's gone from >40 to 5 or less in the last month. I also do a 50% WC once a month. I usually feed twice a day but between the nitrate of this tank and battling brown and green algae in my 40 gallon, (another issue but I'm making progress with less feeding and less lighting) I'd say I probably do 1 feeding a day every other day and feed less when I do 2.

Until yesterday this was an otherwise trouble-free and calm tank. The fish I had up til yesterday were:
7 Neon tetras
4 Ember tetras
3 honey gouramis
2 Pristella tetras (1 of 3 died a few weeks ago after acting strange for a month)
1 Clown Pleco
3 Jilii Cory Cats
2 or 3 ghost shrimps
3 Mystery snails
1 assassin snail
pest snails I'm constantly dealing with. Some like them, I don't.

2 weeks ago I added the 3 Mystery Snails. 6 days ago on Monday I went and looked around and got 3 Checkerboard Ciclids that had just arrived at the store and were just being placed in their tanks. So cute! I bought 3 of them, took them home to acclimate and definitely gave them enough time with 3 water additions. Turned the bag on its side after 20-30 minutes so they could swim out and came back 5 minutes later. One was still inside so I tipped it and he came out, promptly got caught in a bubble and his limp little body just floated around. He was alive, but barely, and was dead an hour later. Another died by morning. That Wednesday I went back and told them about it and hoped to get more. They asked about my PH and told me it was too high for them and I shouldn't get more. I was worried about having 1 lonesome fellow but they said it was okay. I looked around and got 5 Ember Tetras, very lively little fish. This was Wednesday and I was expecting a mail delivery Thursday of some new shrimp. They were 8 Blue velvet and 10 Red cherry shrimp, and I intended to split them between my 2 tanks. So I also bought some Catappa leaves, mineral stones, cholla wood pieces, and wonder shells, to have them ready to help my shrimp find nourishment and places to hide. The shrimp came, and into the 20 gallon I added 3 cherries and 2 blue shrimp. I have never seen the blue ones in either tank since they went in, and I've only seen 1 cherry in each tank since. I am assuming they perished or maybe they're just hiding well. (I don't think so).

Friday, all was well in the tank. Saturday morning we were busy and I got home about 2:30 pm, and immediately saw a dead neon on the bottom, or what was left of it. Took it out, and then saw another dead one, which looked perfectly normal, but dead. Now I'm getting worried and tried to count my other neons and could only see 3, but they like to be in the plants when I'm in there. Sure enough, there was a 3rd dead one. I have never found the 4th body but we aren't done yet. 2 of the new Embers are gone. I got out test tubes and checked levels of everything I had test kits for and that's what's above. Wow, so what happened? I did a 6 gal WC and added Stress Coat, being that's about all I have to offer them. Got up this morning and with room lights, couldn't make out much. I have my lights set every day from 2:15-8:15 pm. Went to church, got back late, waited for the lights to come on, and there was my little ciclid struggling for life, and only 1 neon. Took out my bubbler to have a better look and found what was left of another neon and the ciclid's body, who'd just passed. 2 of my mystery snails were side by side, I can only imagine they're munching on a fish.

So I've lost 6 neons and the 7th is swimming around like he's in an Agatha Christy novel, wondering when he's next (And Then There Were None, for those who don't know the book). 2 Embers are gone, I can't find any remnants. The other 3 look very healthy and active, and I just now fed them frozen bloodworms and they all have an appetite.

Does anyone know what might've happened? Today it finally hit me that something must've come in with a disease; I'd gotten a few new things fairly fast. OR could it be something else?

I'll be taking 2 gallons out as soon as I post this, and hope tomorrow is better.

And new small shrimp - what's the survival rate at any given time? To only find 2 out of the 18 I bought is awful. I couldn't wait to see those red and blue ones in the tanks, and they sure weren't cheap. The ghost shrimps I put in awhile back haven't disappeared but I think I put 6 in and only 2 or 3 remain. 1 survived a molt that I watched, so the water isn't killing them.

There are days that are trying, but today I feel like giving it all away and never doing this again. But I won't. I need to know what happened, what's wrong, and how I move on from here. I'll be cleaning out a 10 gallon tank I've just been growing plants in, and will quarantine from now on.

 

My guess is... if your pH is really high, it could be pH swing effect? That and temperature fluctuations will kill your fish very quickly. Low to high pH is bad for your fish.

EDIT: If you want to know more, you could ask more about it if you want. But if your tank is cycled, I doubt it has to do with that or your parameters. Or maybe your tank isn't cycled, even though it's been running? That could be because it crashed sometime between your starting point to now.

 

Wow. So, would you mind posting which fish are left. Is there any way a toxin got into your tank. I remember a post on another forum-unexplained, sudden deaths. Turned out the OP`s kid got hand sanitizer in the tank.

 

I’m so sorry this is happening to you it’s always scary adding anything new to a well functioning, established tank. Something similar happened to me and I refuse to add anything without quarantining now. I believe this was the problem you have, too. The fish store you got them from has some kind of disease in their tank, as evidenced by a sickly almost dead fish floating right out of the bag.

I really don’t know what to make of the shrimp, I have none myself so I haven’t done any shrimp research, but I have heard on here people saying shrimp are extremely sensitive to changes, so maybe they need a slower acclimation time to really adjust properly.

Since you have no idea what the disease is that they came with, you can’t really use medications unless you plan on bombing the tank with everything you got (last resort only!). Hopefully your healthy, established fish can fight off whatever this is with good, clean water. I know you are on top of your water changes, so keep it up good job there. And stress guard, or adding tannins or anything that helps with stress.

My recommendation for future endeavors into new tank additions is to be very picky about the fish you get. Look at the tank to see if there are any dead fish or sick looking fish. Pick a strong fish from a strong tank. And personally, I’d use a qt tank.

 

It's possible the cichlids brought in something, but they are happiest at 81-86 from what I understand, and a ph <7, so those two things right there aren't great.. Tetras are typically happiest under 7ph as well, so.. yeah a swing could do it.

The nitrates around 40 wouldn't be a huge thing for most fish, some like Cory might show issues with it above 10 even.

Are there differences in the ph from your faucet vs your tank?

As Unknown mentions a dead fish right out of the bag is questionable, but if it happened after you'd added your own tank water? I'd really wonder what's in the tank.

The shrimp? Are likely hiding, they are incredible at hiding. I have shrimp I thought were dead that showed up months later, or like a couple I found IN MY CANISTER FILTER - alive but almost lost as I was cleaning it out in the bathtub... Even when fish eat them there's often little remnants that show up (or so I've found) to signal a death vs. temp disappearance.

 

My guess is... if your pH is really high, it could be pH swing effect? That and temperature fluctuations will kill your fish very quickly. Low to high pH is bad for your fish.

EDIT: If you want to know more, you could ask more about it if you want. But if your tank is cycled, I doubt it has to do with that or your parameters. Or maybe your tank isn't cycled, even though it's been running? That could be because it crashed sometime between your starting point to now.

I really don't think the cycle crashed. I just tried harder to keep it low when the orange started looking more red. I vacuum the gravel more and do more frequent changes. Frankly when it was so low yesterday it shocked me, it wasn't quite to the color of a 5. I just went from an AC20 to a 30 a couple weeks ago but used the same foam and ceramics, so the bacteria didn't change.

Wow. So, would you mind posting which fish are left. Is there any way a toxin got into your tank. I remember a post on another forum-unexplained, sudden deaths. Turned out the OP`s kid got hand sanitizer in the tank.

I just tucked them in for the night and they look fine. What fish are left are:
1 Neon tetra
2 Pristella "
3 Honey gourami
3 Ember tetras
1 Clown pleco
3 Cories

 

So great all look well. Interesting that only Tetra's were affected....

 

It's possible the cichlids brought in something, but they are happiest at 81-86 from what I understand, and a ph <7, so those two things right there aren't great.. Tetras are typically happiest under 7ph as well, so.. yeah a swing could do it.

The nitrates around 40 wouldn't be a huge thing for most fish, some like Cory might show issues with it above 10 even.

Are there differences in the ph from your faucet vs your tank?

I have never checked the PH of water from the faucet! I'll do that tonight or tomorrow - guess I assumed it would be the same.

Thanks for spelling cichlid correctly, as I did not! I've never looked at them before and they're interesting looking. I read a little and it sounds like some varieties come with attitude - these seemed peaceful and curious but I didn't have time to get to know them... I will never try another.

I'm glad my grandkids didn't see them, they weren't in my house today. They always like to go to the fish room to watch them a few minutes and they notice changes. Last week they had some snails and shrimp to watch, the girl was creeped out by the shrimp and they took off. Grandma was creeped out by them at first too but I've gotten to really enjoy them.

As Unknown mentions a dead fish right out of the bag is questionable, but if it happened after you'd added your own tank water? I'd really wonder what's in the tank.

The shrimp? Are likely hiding, they are incredible at hiding. I have shrimp I thought were dead that showed up months later, or like a couple I found IN MY CANISTER FILTER - alive but almost lost as I was cleaning it out in the bathtub... Even when fish eat them there's often little remnants that show up (or so I've found) to signal a death vs. temp disappearance.

So great all look well. Interesting that only Tetra's were affected....

Yes! So far the gouramis and cats look good. Hmm

 

Did the Cichlids kill the tetras? I dont know much about checkerboards. That is a lot of fish for 20g and 2g water changes are not enough.

 

Just reread...in the future, if a shop JUST gets fish in and is willing to sell them, consider holding off. All new arrivals should be in qt with a note on the tank explaining why they are not for sale. If you must have them, you can pay and they will hold until its safe to release them.

And yeah, time for a qt!

 

Yes! So far the gouramis and cats look good. Hmm

Oh yeah, the cichlid type you got looked beautiful, but definitely require a tank setup different than.. most other fish. And as you've learned they aren't the nicest fish at all times. I'd stick to more Honeys personally.

Glad your grandkids didn't see them too! It's really hard to see our finned friends just.. floating.

For ph, I had to learn that the hard way too, my tap was 8.4-8.6 but in my tanks its 6.6-7.4 (max). Big alterations going on in the tanks.

 

It's possible the cichlids brought in something, but they are happiest at 81-86 from what I understand, and a ph <7, so those two things right there aren't great.. Tetras are typically happiest under 7ph as well, so.. yeah a swing could do it.

The nitrates around 40 wouldn't be a huge thing for most fish, some like Cory might show issues with it above 10 even.

Are there differences in the ph from your faucet vs your tank?

As Unknown mentions a dead fish right out of the bag is questionable, but if it happened after you'd added your own tank water? I'd really wonder what's in the tank.

The shrimp? Are likely hiding, they are incredible at hiding. I have shrimp I thought were dead that showed up months later, or like a couple I found IN MY CANISTER FILTER - alive but almost lost as I was cleaning it out in the bathtub... Even when fish eat them there's often little remnants that show up (or so I've found) to signal a death vs. temp disappearance.

Those shrimp are mysterious. I keep foam pre-filters on the intake to avoid things going in, but every time I clean/change them, I find pesty snails in there. I didn't have the right size for the 20/30 filters (same size intakes) so I just got that too before the shrimp arrived so they wouldn't fall off!

Did the Cichlids kill the tetras? I dont know much about checkerboards. That is a lot of fish for 20g and 2g water changes are not enough.

I only bought 3 cichlids (I could look up their long and complicated name next time I'm off my recliner!) but 2 died fast. They're barely over 1/2" long, just babies. He was gentle and spent alot of time exploring the bottom of the tank.

Just reread...in the future, if a shop JUST gets fish in and is willing to sell them, consider holding off. All new arrivals should be in qt with a note on the tank explaining why they are not for sale. If you must have them, you can pay and they will hold until its safe to release them.

And yeah, time for a qt!

That was my first thought when 1 died. They just came in, barely adjusted to new water, were yanked back out and into all new water, that's a lot of change too fast.

But bought on a whim, no research or knowledge about them ahead of time, I accept responsibility for that too.

Dicrossus filamentosus

This is the "checkerboard" - I never did see that nice tail, he was too small!

Oh yeah, the cichlid type you got looked beautiful, but definitely require a tank setup different than.. most other fish. And as you've learned they aren't the nicest fish at all times. I'd stick to more Honeys personally.

Glad your grandkids didn't see them too! It's really hard to see our finned friends just.. floating.

For ph, I had to learn that the hard way too, my tap was 8.4-8.6 but in my tanks its 6.6-7.4 (max). Big alterations going on in the tanks.

You really did bring your PH down alot. I need to learn how to lower it, prefer not to use chemicals. Any tips? If I'd just get it to 7 I'd be excited. And mine is 7.6 because that's as high as my test kit goes. Maybe I should be using the High PH one? Was never really sure when that would be used.

 

You really did bring your PH down alot. I need to learn how to lower it, prefer not to use chemicals. Any tips? If I'd just get it to 7 I'd be excited. And mine is 7.6 because that's as high as my test kit goes. Maybe I should be using the High PH one? Was never really sure when that would be used.

My guess is Addictedtobettas has a low KH (carbonate hardness). The higher the KH, the less risk of your pH dropping, making it more stable. When your pH drops due to low KH, this isn't a good thing. This is a good read... .

Lowering a naturally high pH, is very difficult, much more than raising a low pH, and most people research, and avoid fish that are really sensitive to pH, either high, or low. Most fish will adapt to pH outside of their "optimal" range, but some don't. Keeping your pH fluctuations as low as possible, is the best way to go, rather than trying to make it perfect.

 

My guess is Addictedtobettas has a low KH (carbonate hardness). The higher the KH, the less risk of your pH dropping, making it more stable. When your pH drops due to low KH, this isn't a good thing. This is a good read... .

Lowering a naturally high pH, is very difficult, much more than raising a low pH, and most people research, and avoid fish that are really sensitive to pH, either high, or low. Most fish will adapt to pH outside of their "optimal" range, but some don't. Keeping your pH fluctuations as low as possible, is the best way to go, rather than trying to make it perfect.

I only recently got the kit to measure KH and GH because I had no idea what people were talking about. And I still don't! I appreciate that link and will spend some time learning new things. Thank you!

 

Im still foggy on the Kh and Gh too. At least you can say what it is if someone asks? lol

 

Im still foggy on the Kh and Gh too. At least you can say what it is if someone asks? lol

It's as clear as mud to me too. I know what mine is out of the tap, and what it a week after doing a WC, and a lot of the fish I want, aren't suitable for what my water is, but that's mainly because of my pH being on the high side, running 8.0 to 8.2, more than what my GH and KH are, lol.

 

I want to let everyone know that no more fish have died! I was so afraid to look yesterday morning, but there was my 1 remaining neon swimming around happily, and they all looked healthy and ate well. This morning they're all fine too. Wow what a rough weekend. I'll keep doing some partial water changes. I really want more neons but the next ones will go into a QT for awhile first.

Right now I have 1 neon, 3 ember tetras, 2 pristellas, 3 honey gouramis, 3 Julii cats, 3 mystery snails, an assassin snail and 2 ghost shrimp (and maybe other shrimps hiding) in this 20 gallon tank. I took out a decorative bubbler and have an under-gravel 4" airstone on the right side of the tank near the filter, making a little bubble wall. I like the look of the aquarium better now without that decorative bubbler - there's more swimming space and they can't hide from me - and think I'll move the bubble wall to the opposite side from the filter. (Another benefit of removing it is that I can add that much more water - this 20 gallon looks half full when I remove 8 gallons.

Someone said I had too many fish - at one time I had 28 in here! After I got the 40 gallon, many moved there. All my honey gouramis are male and I'd like to get 1 or 2 females. When I'm in the fish store, I can't figure out the sex of them and they say they can't tell either. Really? (I've looked at pictures online but still can't tell when I'm standing there, they don't stay still long enough!) Anyway, I'll probably order a couple online because they aren't always stocked here.

So if I get 2 more gouramis, how many neons should I add? Since I got my nitrates down, I really don't want to overcrowd. Neons are a schooling fish, I don't want him alone. I'm willing and able to move the pristellas over to the 40, I have room for 10 more fish there.

 

That's great that things seem stable now. Very glad to hear you'll be holding off on adding anyone more for awhile and will qt first.

"1 neon, 3 ember tetras, 2 pristellas, 3 honey gouramis, 3 Julii cats, 3 mystery snails, an assassin snail and 2 ghost shrimp (and maybe other shrimps hiding) in this 20 gallon tank"

Please reevaluate this stocking before adding anyone else. Your tetras and corydoras need to be kept in higher numbers to reduce stress. Or rehomed/returned. Make sure everyone in your tank is happy in the same parameters-ph, temp, flow, required hiding spots...

 

That's great that things seem stable now. Very glad to hear you'll be holding off on adding anyone more for awhile and will qt first.

"1 neon, 3 ember tetras, 2 pristellas, 3 honey gouramis, 3 Julii cats, 3 mystery snails, an assassin snail and 2 ghost shrimp (and maybe other shrimps hiding) in this 20 gallon tank"

Please reevaluate this stocking before adding anyone else. Your tetras and corydoras need to be kept in higher numbers to reduce stress. Or rehomed/returned. Make sure everyone in your tank is happy in the same parameters-ph, temp, flow, required hiding spots...

The fish combination I had were all very happy in there until I brought those cichlids in - they will never grace my tank again.

I have the 3 cories, should I add a couple more with them? And would they be better with 2 more Juliis or any variety? In my 40 I have 5 albino, 2 peppered and 2 bronze and they all hang out together. I only had 1 bronze and brought a baby one home a week or 2 ago, and it was really something how he hung out immediately with the other one! I like the albino especially in there since I have black sand.

Anywho... how many tetras would you recommend? And the embers I have 3 of, should I add a couple more? As I said, I can put the pristellas in the 40 to make room, I won't be getting more of them.

Thanks so much for your thoughts! Have to leave for a few hours, will read later.

 

I suggest seriouslyfish.com as an excellent resource for confirming compatibility and requirements-temp, tank size etc.

Tetras and corydoras do need to be in larger groups. 6 of each species is universally considered acceptable but I've never discovered who came up with that and what the number is based on. Would love it if anyone could share a source for that info.