Was watching my fish today and i noticed that one of the brinze cory's is missing parts of his dorsal fin and part of his the top of his tail fin, now as far as i can tell all the other fish in the tank including the other cory's are all happy and healthy, and its not fin rot (again as far as i can tell) is it likely he is being picked on? as i said in a previous post when they were introduced to the tank the male dwarf gourami i had was going for the new gourami i introduced (he went back to the shop) and he was being nippy to the cory's, that was about a week ago. and everything seems to have settled down in the tank (though the cory's steer clear of the gourami. so are thes old wounds or is he still getting picked on

Can you post current test results please: ammonia, nitrite, nitrate and pH?

If possible, post a pic of the damaged fins, or if you can't, can you describe the damage in more detail?

ammonia nitrate nitrites all 0ppm

ph is between 6 and 6.4 according to the api master test kit.

and cant get a picture up sorry but the fin is all jagged, clean but jagged if that makes sense

Sounds like fin-rot is potentially possible as your water readings show the tank isn't cycling fully or your test results are off. Nitrate shoul never be at 0 in a cycled tank as it is the inal product of the cycle and is only removed by water changes. It would take a 100% water change with water that has no nitrate conmtent at all to get a 0 reading on a unctoning tank. Which test kit are you using?

Also your pH at only 6 to 6.4 (you need to be moe accurate) is a problem. Your original tap pH was over 7. or it to have droppe to such a low level is concerning and it may have dropped low enough to stall teh cycle. It's important to in out why ther pH has dropped, why there is no nitrate present and to watch o potential ammonia/nitrite spikes. You also need to work out whether your test kit is functioning correctly.

the ph has dropped because i dropped it on purpose to keep the eber tetra's and the ph in this tank has always been between 6 and 6.4 but i think i may have managed to kill all the bacteria i had in the tank some how is that posible? i recently changed the substrate so maybe that did it?

How did you lower the pH? Was it with a chemical?

yeah i used API ph down

OK, that's the problem. pH Down works by dissolving carbonates (kH) to lower pH. When carbonates go too low, the bacteria die as they need carbonates to function and do their job. This is one of the reasons chemical adjustment of pH is not a good idea.

that would explain it, damn well ive just taken another set of reading ammonia .5 ppm nitrate 10 ppm needless to say ive just done a 25 % water change, so id say my tank is still cycling but i dont get the ammonia spike? defo in way over mu head here

Very briely ...carbonates in the water make pH stable and hard to change, they also determine how high pH is. The bacteria that process fish waste do so by a chemical reaction and part of the way they do it is by using carbonates in the water. This is one of the reasons why we do partial water changes - to replenish carbonates and maintain pH. When carbonates are used up, the bacteria stop working - a symptom of exhausted carbonates is falling pH levels.

When pH is lowered by using cehmicals like pH down, they do so by dissolving the carbonates in the water. If too much of the carbonate is neutralised by pH adjusters (basically they're just acid), then there isn't enough to allow the bacteria to do their job. They then die off and ammonia is no longer processed, resulting in a spike and an uncycled filter.