pappy

I have a 55 gallon freshwater tank with a bio-wheel 350 filter. It contains two albino oscars, a Florida gar, and a pim catfish (I think that was the name of it). Until yesterday it also had a pleco. I do a weekly 20% water change during which I vacuum the gravel. The past three weeks the ammonia levels have jumped from safe to toxic after this water change. I have been using Prime to condition the tap water before putting it in. I have gone through two plecos because of this, I believe. Anyone have any suggestions? Thanks.

Lucy

Hi pappy welcome to Fish Lore
Two Oscars is quite a bio-load for a 55g, throw is the Florida Gar, who needs a 200g tank, you're way overstocked.
I imagine the bacteria just cannot keep up with the bio-load in your tank.

It would be a good idea to at least increase the amount of water changes you've been doing and re-home the gar.

Good luck

pappy

Thanks for the advice. Just out of curiosity, why does the ammonia spike when I change the water and vacuum? It seems as though that should have the opposite effect.

Lucy

It should, unless you're stirring up a bunch of stuff.
Have you tested your tap water for ammonia lately?

cerianthus

Very simple.
If no ammonia were detected for weeks but spiked after pwc
1. New water had chloramine and conditioner broke the bond b/n them, will produce ammonium ion (NH4+). If pH is higher7.6, NH4+ will convert to toxic Ammonia (NH3).

2. Maybe vacuuming may have removed much needed or should i say well balanced bacteria with such loads as yours in 55G.

Next time why not vacuum only 1/5 of the bottom surface area with pwc and alternate the area with each pwc thus minimize the disturbances of well established balance.

I do know tank will harbor enough bacteria no matter how overstocked it maybe. It just takes time to establish. Once established/cycled, do minimal disturbances to such system at a time and have garbage containerful of well aged water ready to at all time.

3. sudden drastic changes in tank's ph can also affect the activities of bacteria.

I am sure there are other possible reason but getting too late and cant think too straight.

Try to keep record of testing including pH before and after pwc. I think too many people overlook this issue. Still some argues it is not important where fish will adapt. Yes it can but how much. We will never know how each individual fish can tolerate the difference.

Dynamics of water chemistry is very difficult subject and I dont think I understand to its fullest even with chemistry background but do know pH plays very important role or should I say affect other substances. It also have direct effect on the fish with fish's respiration and excretion, dermatologically (did I spell that correctly?).
Look into Physiology and/or anatomy of fish and will learn quite a bit which you can apply to hobby. I assure you, you will do lot better, not just its husbandery but with spawning and rearing.

Hope tank settles soon w/o further mishaps. Good Night!