Help and advice: Fish dying in established tank
I have a 29 gallon freshwater tank. The tank was set up 6 months ago, and up till now we haven't had any problems with the fish.
Our tank consists of mostly platys, one goldish, several neons, several catfish/corys, and one bamboo shrimp- all very mild mannered and get along great... about 15 in all. We have had them all together for 3 months with not one issue.
I test the water regularly, and in the beginning we had some issues getting the ammonia to zero (kept read low levels at .25 and .50), but after a proper cycle we have not had any issues at all with the ammonia. Even today, the ammonia read zero. Nitrates, Nitrites, in safe zone. No chlorine. Hardness is on the low side and always has been. pH always at a neutral level. Alkalinity on the low side. No live plants in the tank, just plastic.
Water temperature is consistent at 78 degrees. We have been doing weekly water changes, about 30-50% each time. With each change, we add Prime.
Yesterday, my husband and son brought home two new fish (red eye tetras). They were introduced to the tank properly, but we found them to be too aggressive in the tank so we isolated them. Not before they terrorized a few fish. It took awhile to get them with the net because they were so fast, and I am nervous that I freaked out the other fish trying to catch them.
I removed a few decorations in the tank while I was doing this and found two dead fish... now whether is was coincidence that they died, or the tetras nipped at them, I will never know. I decided to test the water after this, and noticed my pH was very low and water was showing much more acidic than normal. No ammonia.
Fast forward 5 hours... I go home and find my goldfish, a panda cory, and a platy are dead. I feel horrible, I don't understand what went wrong. It's as if the tank changed overnight.
What happened? How can I keep my other fish alive? Some look fine others look lethargic. No sign of disease, water is clear, but something is going terribly wrong!
I would guess the sudden shift in pH is to blame, not the momentary rudeness of a couple red-eyed tetras. Is it possible that a rcent water change was carried out with water from another source or that your local water out of the tap was treated, suddenly, in a new way. This issue came up recently on another forum, and these unexplained drops in pH and associated fish deaths occurred without any sign of disease, and it was determined that nearby water treatment had lowered pH.
You are aware that a full size goldfish would make short work of neons, right. They aren't mean, just opportunistic. Do not put another goldfish in with the other fish you have.
I believe it is good that you removed the red-eyes. Should have been purchased in a much larger group, but also placed in a longer tank, I think, owing to their very active swimming style and larger adult size. If you want more fish, and space allows, I would add to the neon or cory population.
We have city water, and I did have the thought that something may have changed with the water coming into my house. Even though the water is treated, the problem is it is treated, so, yeah, I am doing not another experiment testing the tap water.
Is there anything I should try to increase the pH, or just continue with frequent water changes?
I agree, the tetras are a bad idea. Of course trying to explain that to my husband and son proved difficult, but now they know.
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I agree with sidluckman but I also think there may be more at play here. This will take some explanation, so bear with me as i want to help you to understand things and be able to have healthy fish.
First, can you give some numbers for nitrite, nitrate, and GH and KH (alkalinity)? "Safe zone" may mean different things to various aquarists, and may not be so safe. For instance, if your GH and KH are low, the pH will be subject to fluctuation and tend to lower, this is perfectly natural and normal although it may have dire consequences for the fish. I can explain this further when I have the numbers. Also, a low GH is causing trouble for any livebearers (the platy), so this is another issue, and the pH lowering below 7 is making this worse for them.
But don't jump in to fix the pH, this also can backfire; the GH and KH are connected, and when I have the numbers I will be able to suggest the safest and best way to raise these. Although your soft water fish will then have difficulties.
Nitrite is highly toxic at any level above zero, so knowing the number here is critical. And nitrates affect all fish at any level above zero, even though many will still accept nitrates above 20ppm or 40ppm as OK. They are not.
As sid mentioned, the fish combination is causing stress even though you may not see it in physical terms.
Al of these things stress out fish because they make their everyday life processes more difficult, and this in turn causes further stress which adds to the problem and weakens the fish. One otherwise small stressful issue, like introducing a couple of new fish that are not exactly docile, can be the straw that breaks the camel's back.
Thank you Byron. Ok- I just bought a new API freshwater test kit. Here's what I have:
pH 6.0 or maybe less... The reading bottomed out at the lowest part of the scale provided.
I did another 40% water change after I tested. I also tested my tap water. I aerated it, let it sit for about 6 hours, and when I tested thar, the tap water pH was 7.6.
I have not added anything to the tank except Prime. I saw a litany of items at my local fish store, but I didn't want to buy/use anything I haven't researched. Maybe extra water changes are the smartest move? If my tap water is ok pH wise, why can't I keep the tank with that same pH?
Also, since last night, I lost one catfish Cory and one glofish.
This is what remains in stock: 2 glass catfish, 2 panda corys, 3 platys, one neon, 2 penguin fish and my one bamboo shrimp. The platys look lethargic, the others are acting normal.
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I'm sorry you contine to lose fish. Byron's assessment seems accurate to me. I fear I am out of my depth to advise you further, and will contunue to monitor this thread for my own benefit. . .
Thank you sidluckman, I appreciate your comments.
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But in the interim, I will surmise on why your pH is lowering. I am assuming you have fairly soft water, with a fairly low KH (carbonate hardness or Alkalinity). The KH works to buffer pH, keeping it from fluctuating; the higher the KH, the more it will buffer. In such a situation, the pH of the tap water will be identical or very nearly so in the aquarium. But if the KH is low or even non-existent (as my tap water is), then the pH will naturally lower as I'll explain below.
As fish, plants and bacteria respire, they give off CO2 (carbon dioxide). Even more CO2 is released during the breakdown of organics (fish waste, any dead fish or plant matter, uneaten fish food, etc). As the CO2 enters the water, it creates carbonic acid, and as this increases it acidifies the water so the pH naturally falls. This is a perfectly normal and natural process.
If the KH is sufficient to buffer the pH, the accumulation of carbonic acid cannot affect the pH. But if the buffering capability of the KH is low, the pH will lower. I assume this is what is occurring in your tanks, as it does in mine, and every aquarist's who has source water (tap) with a low buffering capacity.
Now, there are other factors that can affect this, and pH directly. For instance, substances that target the pH. Wood, peat, dry leaves all release tannins which soften the water and lower the pH by much the same process as above. On the opposite side, calcareous substances (sand, gravel or rock that is limestone, marble, dolomite, coral, lava, aragonite) release hard minerals and KH into the water and thus work to raise the GH and KH and corresponding pH.
I have tried to simplify this here, but you may find my article helpful for a bit more detail:
So, along the lines of the above, the more fish in the tank, and the more food they are fed, the more organics will accumulate and increase the natural pH fall, again assuming there is little or no buffering capacity.
Adding pH adjusting chemicals will usually not work long-term because they do not take into account the extent of the buffering, which is obviously unique to each aquarium. So stay away from these. I still want to kn ow the GH and KH, otherwise we are just guessing. But we also need to know what fish you want. As I mentioned previously, livebearers require hard mineral in the water, and they will suffer with this low a pH and (probable) GH. The soft water fish (tetra, etc) will be fine. If you do take steps to increase the GH and pH, this will improve things for the livebearers but depending how high these go it could make life very difficult for the soft water fish. This is why it is so important to research all fish beforehand, to know the preferred water parameters. There is no "middle ground," as someone will always lose out. However, the are many fish that can manage in a slightly basic medium hard water with the livebearers.
Great info Byron. I just tested again this AM, pH still at 6.0 (or less). GH 20, KH 0. Nitrite and Ammonia still at 0, nitrate still at 10ppm. Yes, our water is very soft. We do not have a water softener in our home, the water we use is from the tap, so whatever our municipal standards are, thats what I am stuck with.
So, is there something I can add to raise GH and KH?
What types of fish will work well in the environment I can support? It appears the catfish and platies have held on through whatever happened this past few days...
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Now, you have two choices. First is to stay away from hard water fish like all livebearers, and stock with soft water fish (almost all the characins, many catfish, dwarf cichlids, many of the cyprinids, the badids, the anabantids...there is a literal world of fish to select for soft water. This is what we term choosing fish suitable to your water. It is the easiest, because you can use what comes out of the tap with no fiddling, and the fish will love it.
Second choice is to raise the GH and KH and pH up to some level that will suit livebearers and a few other fish. Some of the so-called soft water fish can manage with this--among the characins for instance the Pristella Tetra. But many, like cardinals, neons, the rosy clade, etc will not do as well--same problem for them as now for the platy, only in reverse.
I mention in that article the safest way to raise GH/pH, and that is with a calcareous sand or gravel, either in the filter or as a substrate. The latter will result in very hard water with a pH above 8. Using this in the filter is a bit more experimental. I have tried this, and gave up because it raised the pH astronomically compared to minimal for the GH. The substrate method as i say works, but this is only suitable for livebearers and rift lake cichlids.
There is another issue though, and that is live plants. You will not have sufficient "hard minerals" (calcium, magnesium primarily) for most plants. I solve this problem with Seachem's Equilibrium. It raises the GH by adding calcium, magnesium, potassium, iron and something else i can't remember at the moment, and I have it down now to where i use a measured amount after every water change to maintain a GH of 5 or 6 dGH which is sufficient for the plant but not enough to bother soft water fish. Equilibrium has no effect on KH or pH. I let the pH do what it likes.
I can elaborate if asked.:-)
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