What just killed all my fish?!

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You could speed up the cycle by transferring some of the media from your other tanks into the filter of this tank (assuming your other tanks are properly cycled). How long have your other tanks been running?
 
I have spring water and the PH is 7.0 and I have never tested for hardness. I just assumed that because it’s spring water it’s not “hard” but I’m taking a vial to my LFS in the morning and going to have them run full panels
 
I am nowhere near an expert, but the ph up could have caused irritation on the fish and it might be excess mucous.
It killed my loaches, a molly, and some guppies. I have had over 20 fish die just in the last 3 weeks and all for different reasons. It’s one thing after another. I’m nuking this tank and starting over.
 
There is a kit you can buy to determine the GH (general hardness) and KH (calcium level) in the water but I don't think it's worth worrying about since this sounds like a PH issue. . I think for guppies which are kind of adaptable compared to other species I would worry more about the PH fluctuations. Try this -assuming you are on City water = go to your City's website and to their water department. Most water department annually publish a report of the water properties in your city. It has WAY more than you need to know but it also usually lists the General Hardenss and the KH for calcium. And it should show both the range and average PH for the water in your city. Most likely your tap water parameters are pretty close to the averages listed here. Now if you are on well water you'll need to do the testing yourself. But by using the water report you'll save a lot of time and money on test kits that you'll use once in a blue moon.

Here is why I get concerned about PH - Our city average PH is 9.4. Nearly all freshwater fish require a PH between about 6.5 and 8.5 depending on the species. I think guppies need a PH between 7 and 8 - probably closer to 8 since they say they prefer alkaline water. Suppose you look at the water report and find that the average PH in your city is 6.0. Not acceptable for guppies so you can either try a different species or you can adjust the PH in the water. My fish all do best with a PH of 7.0 so there is a product on the market that neutralizes the PH in the water and adjusts it to exactly 7.0. Unfortunately for some other chemistry reasons we won't get into - it does tend to start drifting downward during the week but since I do weekly water changes my PH will have just wandered down to 6.5 when I do a water change with water that has been PRE-ADJUSTED to 7.0. I'm not going to dump PH 9.4 on the heads of my fish and THEN add the PH adjuster. If you change water by buckets adjust each bucket (and PH up is fine) to the PH you need and then add it to the tank. The easy way to do this is to measure the PH in your bucket of water and guess about now much PH up you'll need for each bucket to get it to 8.0 - it's kind of trial and error. Once you know how much it takes you can just use that same amount for each bucket without testing every bucket of water. It's kind of frustrating but once you settle on a routine you won't need to worry about measuring the PH as frequently. Before you do that you want to get the water in your tank to PH 8. That doesn't mean just drop a capful of PH up in the water, but pull out about 1/2 gallon and mix the PH up with that water so you are diluting the effect of the PH change - fish don't like fast PH changes, that's why I mix my water before adding it to the aquarium.

Another possibility - could you have accidentally forgotten to add a water conditioner like Prime before you did the water change? That will kill some fish faster than anything else. The water conditioners remove chlorine and chloramines from your water. This should be added to every bucket when you do a water change (just a few drops). Twice in 4 yrs I have done a water change and just suddenly started seeing about 1/2 my fish population just drop dead in the water. My assistant swears she added the water conditioner but it's easy to take your mind off what you are doing and forget to add it (if you can't remember, just add some more - it won't hurt anything). That actually sounds kind of like what happened to your guppies rather than a PH issue - without the PH data it's hard to tell. But each time I only lost about 1/2 my fish, some fish just adapted to it until we could add some more to the water, take PH readings etc. We will never know exactly what happened but it shows you how critical it is to pay close attention when you do a water change.

I would also go to the pet store or order from amazon some nutrifying bacteria - I like tetra safe start plus. It's a water conditioner plus bacteria. Add 1/2 to a whole small bottle depending on your aquarium size. This is because you didn't cycle your tank, but I've cycled a tank in 2 days using this stuff - I rushed it. But plan on not adding more fish for at least a week. Get a API test kit that measure ammonia, nitrites, nitrates, and PH (it's cheaper to buy the full kit than a single test) and if you see you have an ammonia spike (which I'm sure you do right now), start adding PRIME every two days to temporarily control your ammonia and nitrite levels. You'll have to add a capful every two days until the ammonia and/or nitrite spike is gone. Now the bad news about using Prime to do this is that even though it is REALLY controlling your Ammonia and Nitrites (for 2 days) they will still test high on your test kit. If it's an ammonia spike (and with all those dead fish in the water it will cause a huge ammonia spike) it will keep it under control. Eventually your tank will start the Nitrogen cycle on it's own, you'll just have to monitor the water closely. (Oh and after removing the dead fish do another 70% water change and then measure the ammonia and nitrites) But once you see your Ammonia levels drop while your nitrite levels rise you will know your tank is starting cycle on it's own. A few days later (with the help of that bacteria you bought) you should see your Nitrites drop and your Nitrates rise. At that point do another water change and retest everything - if you have zero ammonia and zero nitrites you are likely good to go - thanks to that bottle of bacteria. But only add a couple of fish at a time, or you'll find you don't have enough bacteria to cover the dozen new fish you just purchased and the whole nightmare with start again. This is the cheaters way to cycle a tank - and I still recommend if you start a new tank cycle it the normal way (but add the bacteria) the bacteria will take the cycle process down from 6 weeks to about 2 weeks. Again, bacteria take time to grow so add fish slowly.

That is everything I know at 2:30 am. And I'm sure some people hate cheating on the nitrogen cycle - but you kind of have a special case. Good luck.
 
Don't nuke the tank - work with it and get some bacteria in there, do that water change and buy a test kit. No point in giving up. Losing that many fish so close together I'm thinking this was either due to a big ammonia spike (due to dead fish in the water and no water change being done) or you forgot to condition you water when you did the water change. I think my assistant and I have accidently done that twice in 4 years and each time lost half our population. Made us just sick. We'll never know for certain but that was our best guess. Remember ONE dead fish in the water for a couple of days can cause an ammonia spike as their bodies decay - so always check your populations daily to make sure somebody isn't mysteriously "missing". If the other fish eat the dead fish quickly it's really for the best (other than getting the fish out of the tank as soon as you see it is dead).
 
Read up on the nitrogen cycle and make sure you understand what it's trying to accomplish and then use your brain to see how you can accomplish it based on your current tank parameters. That will give you some insight as to why you can have a mass die-off and other disasters. But don't just follow instructions really THINK about what you are trying to accomplish. You have a brain, use it.
 
We had no idea what a biological cycle was. Both of us (my husband and I) have had fish tanks before and had never even heard of it.
Science is a wonderful thing...we can now keep our fish alive for much longer and in a generally better condition. Diseases amongst those in the know are hardly ever encountered and we don't need to spend a fortune on medicines.
Growing up, my parents bred guppies and mollies and never had a fish die, save for old age and they never added anything to the water nor did they use a test kit or do weekly water changes.
Guppies are known as 'millions fish' for a reason. ;) That said, I'd guess the guppy life span was significantly reduced, as compared with what it could've been. In the Olden Days, fish simply living was seen as an achievement. We now know better and do better.
We just did what the guy at Pet Smart said (which is unfortunate and has caused great loss). He said to add the bacteria and a couple goldfish and wait a week before adding anything else 🙄
That guy was an idiot and should be sacked. His goal was to make money, at the expense of living creatures and your good selves. The very idea of 'a couple of goldfish' implies that he viewed those as expendable. 'Goldfish' are coldwater fish and have their own very specific needs, few of which can be provided by a tropical tank set-up. Not only has he cost you money, he's caused suffering to fish and anxiety to you and yours. :mad:

To answer your repeated question about the 'white scummy stuff'...
Without knowing about your tank size, water parameters and other fish species present (and in what numbers), I'd be guessing. It could be anything from bacteria, fungus, or, as has already been suggested, excess mucus, whilst the fish struggled to survive in toxic water. :(

The way forward...
  • Lots of water changes, using conditioned water.
  • Acquire and use a quality test kit, such as that offered by API's Master test Kit. This puts YOU in control and, believe me, any excess levels can always be reduced by something as simple as a water change.
  • Having siphoned off all visible waste, fasting your fish for 24 hours wouldn't do any harm. Any future feeding should be cautious.
  • Use an air pump and add aeration with an airstone or two.
  • Adjust your filter to agitate the surface of the water.
  • Add plants.
Since returning to the hobby, I've discovered the bottled bacterias and, from my own experience, I've been pleasantly surprised, (I use the Microbe-Lift Special Blend and Nite-Out II). That said, I cycled my well-planted tank without fish, using old gravel with an old, organic content and had fish in by week 4.
 
Just to confirm - there are no fish left alive?


Going forwards -

Yes, get your tap water tested at the LFS. Make sure they give you numbers for hardness (GH) and carbonate hardness (KH) and not some vague words. Also ask them for the unit of measurement as there are several they could use.
It is important to choose fish which come from water with roughly the same hardness as yours. Once you know your GH, you'll know what type of fish to look at. KH is also useful because that buffers the pH against changes. When KH is very low it can all get used up leaving nothing to stabilise pH. This may be the cause of your pH drop.

Buy a liquid reagent test kit so that you can test pH, ammonia, nitrite and nitrate for yourself.

If there are no fish left alive, I would thoroughly clean the tank. Drain all the water and clean the gravel at the same time with the siphon tube. Then refill with water which has water conditioner added.

Are the plants in your photo live or synthetic? If they are live, you could add a lot more and wait till they are activeley growing then add fish a few at a time. This is called plant or silent cycling. If they are fake, you need to do a fishless cycle following the link that Fishmanic gave you in post #6



When you've had the water tested for GH, could you post the results here please. Members will then be able to help you choose fish suitable for that GH. And can you also tell us the dimensions of your tank (length width and height) so we know which fish will fit.
 
Yes, get your tap water tested at the LFS. Make sure they give you numbers for hardness (GH) and carbonate hardness (KH) and not some vague words. Also ask them for the unit of measurement as there are several they could use.
Given the 'care' already given by that local fish shop, would you really trust them to give accurate info? I'd just buy my own testing kit/s (as has already been suggested) and do it myself, just to be sure. ;)
 
Or a visit to a proper LFS not Pet Smart.
Unfortunately, we do not have another LFS near us 😳 we have to drive almost an hour to get to another fish store. We’ve done it many times before but it is not always an option for us. (We have a newborn)
 
Unfortunately, we do not have another LFS near us 😳 we have to drive almost an hour to get to another fish store. We’ve done it many times before but it is not always an option for us. (We have a newborn)
My nearest quality shop is just over an hour away. Fortunately, I have a quality set of test kits, so I'm not dependent on others to tell me what state my water's in.
 

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