You mentioned previously that you had high ammonia levels after the
incident. I'd keep doing changes for at least 2-3 days past the point
when the ammonia drops back to what you would consider "normal", and
even below that. Yeast and sugar in a nice warm tank? The yeast will
love that!!

Well normally i have zero ammonia and nitrites. I did another change
yesterday and no more ammonia or nitrites. I've put in some carbon
filters as well and some fine filter media.

My Angels have reddish fins now which are getting better. I understand
they could have nitrites burns?


Also, when doing the change, i cleaned the filter media (in tank
water) and it was really really slimy. Do you think i might have an
algae problem as well?

How often do you clean/change the filter media? Slime happens over
time due to trapped food particles etc. in the filter media.

I usually do water changes once a week and clean the filter media when
doing water changes. I don't "clean" clean; i just make sure they
aren't clogged up. I mentioned the slime as the media isn't usually
slimy.

I've also just discovered that adding co2 to a tank drops the ph. I've
been looking at getting a pressurised co2 kit. I went to my local
aquatics shop and went through all the different types of kit
available, regulators, ph solenoids etc. Looks like I'm going to be
spending about 200 squid on new gear! I also didn't realise that just
injecting co2 can cause a ph drop to 4 or 5ph which would definitely
kill all my fish! So when I've got enough dosh I'm going to invest in
the ph regulator.

Also, i didn't realise that you should turn off co2 injection at night
as plants expel c02 instead of using it at night?

Thanks for everyone's help.

Also, why have all my shrimps died? Are shrimps more susceptible to
contaminates?