[NavyWifeKimee]

I have had a 75 gal freshwater tank for awhile now. I never do any water changes except for when I have had these kind of problems and I need to know what im missing and what i need to do to fix it. Ok so for starters I have had just random fish die. Some will last for a year some will last less then a week. Out of no where. Never showing any signs. Which in turn makes me have to buy new fish over an over. Another problem I have had and currently do is my fish are swimming to the bottom of the tank and just pointing downwards. Now they will move about the tank at random occasions but then return to their school and face downwards. What I have noticed today is now they are still as can be at the corner of the tank at the top of the tank..... very odd. My bottom feeder tend to freak out every now and then and likes to dig a lot. The diging I find to be normal but now the ziping around the tank and swimming and breathing fast. I know I have had in the past a very slight amonia level but nothing to worry about and has been the same since the begining of this tank. I do not make water changes but do keep my filters clean and add water treatment when I refill the tank. Please help! I have some few lon lasting fish in there I would hate to loose. Maybe if someone can tell me in detail how to stay on top of this tank so I can stop having issues repeat and loosing fish all the time. Or point me to a site. Please and Thanks so much for your help!

 

[Boredomb]

To me it sounds like you tank went into Old tank syndrome more or less. This happens when you don't do water changes and over time if the ammonia builds up the Ph will drop in tank. Old fish in the tank can usually seem fine as they are use to it but when new fish are added they will not make it. Over along enough time the old fish won't make it either due to ammonia. This one of many reasons why water changes in the aquarium are soo important.
http://www.tropicalfishkeeping.com/freshwater-general-articles/regular-partial-water-changes-188641/

 

[Chesh]

Hi, Kimee! Welcome to TFK!

Bored is right, it sounds like Old Tank Syndrome to me, too. . .

Pay special attention to section #4 in the article that he linked you to, I've dealt with OTS in a couple of tanks that I stepped in to 'rescue,' and you'll want to be very careful to move slowly with water changes, and not to replace too much water too quickly, or the fish may not survive it. The old fish have lived in this water for some time, and though the water quality isn't ideal, they've adapted to the toxin/Ph levels in the system. It can be just as much of a shock to those fish who have lived there longest to be brought suddenly into very clean, fresh water as it is for the newly-purchased fish to be dumped into a tank with old water, especially since they're struggling already.

Once you get the water quality back to where it should be, it's best to do a single 30-50% water change every week, but I'd start with smaller, more frequent water changes until everything is back to where it should be!