It's possible if either:
Your doing it daily & removing the fish etc and over stressing the fish
Or more plausible,it's a filtered tank and your cleaning all the deco and changing the filter media (and thus removing all the bacteria of a cycled tank) while doing the water changes of a cycled tank.
More info is needed to agree/dismiss this theory.What size tank,filtered or not,how regular are the water changes,how much water are you changing,how many fish,how long have you had the fish etc etc.
Sorry. It's a 14 gallon filtered tank. I was doing weekly water changes but I've slowed down to once every two weeks (although that still hasn't helped. Another fish just died. =[). I try to only change about a tenth or so of the water every time. Sometimes I do a little more, but not too much because I don't want to take too much bacteria out. I haven't had these fish long, since the fish that I put in my tank tend to die. A few months at the most. I do have a pleco and a loach that have been in there for about 8 months and seem to be the only ones thriving. I change the filter once a month. I don't take the fish out when I clean the tank, and I don't take the deco out. I just use the gravel vac and get up as much gross as I can without taking out too much water. I make sure to get any food that's not eaten on the same day that it isn't eaten so that it's not just sitting there in the tank, and I try to remove any dead animals as soon as I notice they've died. So far, I've had several platys (I've lost count of the exact number), 3 snails, and a catfish die (not all in the tank at the same time, of course, but over the last 9 months or so). I don't know why they keep dying; I'm really not trying to kill these animals I just want to give them a home. Unfortunately, my home fo them seems to be causing their deaths. =[
You can over clean, however, I don't think that is what is causing your fish deaths.....in a 14gal filtered tank I would be doing 50% with vacuum weekly to maintain water quality in a properly stocked tank.
How soon after you intro the fish do they die, do they show any signs or symptoms before death, how do you acclimate them, what is your stocking level and species of fish, any live plants and do you have any water pram numbers for ammonia, nitrite, nitrate, pH and if so, what kind of testing products do you use, additives used.....
1/10 water changes every week is not enough IMO. Definitely do keep up with weekly water changes, but I would suggest something more along the lines of 50%. What kind of pleco, and what kind of loach? They may outgrow your tank. Have you tested your parameters? There may be something off there. You also could have a problem with the source water, or you could have had a fish with a contagious illness that just continued to spread.
I do 30% changes with my goldies. 100% in a cycled filtered tank is a bad thing, but 10% may not be enough.
Definitely check your water parameters. Are you removing all the chlorine, copper, etc from your water before putting it in the tank?
Is there a pattern to the fish deaths? Right after water changes, always on Saturday afternoon, when your neighbor sprays weed killer on his lawn? Anything like that to help you pin down what is happening?
Wow there are so many replies... I don't have the answers to all of the questions but I'll do my best.
There's no real pattern to the fish deaths. Sometimes they're a couple of days after a cleaning, and sometimes I find them dead when I'm cleaning. I found two dead ones while I was cleaning the tank once. There's no real pattern to how long they're in the tank before they die, either.
I have had my water tested a few times, and each time the people at the fish store say that my water is fine; the only issues I have with my water is that each of my tanks has a different pH (even though they all have the same source water). Not sure what that's about.
I'm not exactly sure on what type of pleco and loach I have. The pleco is one from a local fish store, and the loach... well I remember that we chose it because it was supposed to be able to fit in the 14 gallon. I don't remember what the specific types are, though.
I have no live plants, they're all either plastic or silk. Um. Right now I have 3 danios, 2 platys, a ghost catfish, my pleco and my loach in there. Did have 3 platys but one just died. Am I overstocking it? My pleco is getting a little big, maybe that's an issue, too. I just added the danios about a month ago, not too long before the last platy died.
So... maybe I'm not cleaning my tank enough? There are probably a few issues that are causing my fishies' deaths. I'm just not adding anymore fish until I get it down pat. Plus, I'm moving in a month, so adding fish would be bad anyway. Plus, it'll probably be overstocking the tank. =/
My 10-gallon tank is down to one mollie, one full-grown high-fin platy and a baby fish (a couple babies randomly popped up a couple weeks after I bought several high-fin platys and one of them somehow survived), a clown pleco and two cory cats. Three of my platys died, but probably from the mollie nipping at them whenever I tried to feed them. How the rest have survived, I don't know. Sigh. My fish problems are many. Maybe I should take a break from adopting fishies. =/
Hmm, what type of water are you using? (tap, RO, etc.)
Also, sounds like you need to rehome the pleco. He's most likely a common one which needs atleast 55 gallons, maybe more, each. They get HUGE. Also, some species of loach also get huge. WAY too big, (I believe one gets over a foot? Not sure about that, but some get way too large for 14 gallons) Did you cycle the tank first? Also, don't trust the fish store. They might be using testing strips which are very innacurate. And, to a fish store employee, 2 PPM ammonia and 6 nitrite and 60 nitrate might be fine to them but deadly to their fish. You should get a liquid "master" test kit, they tend to be accurate and last forever.