I have two tanks (out of my 11) which always seem to have cloudy water. All 
my tanks  are at least 12 months old, all are established and all fall well 
within the "good water parameter" borders". all are filled via the same 
water supply with the same water conditioner, yet still two remain cloudy. 
One is my gourami tank, holding half a dozen various gouramis, all over 12 
months old, and 2 clown loach as well as  bumblebee gobies - again all over 
12 months old.
The other is a small tank originally kept for breeding killies in, that 
currently holds a fairly ancient angel fish and 4 baby (2 month old) danios. 
Plants grow well in both, the gravel is well vacuumed every so often in 
both, here's definitely no dead fish - so why are they, and none of the 
others (cold water and topical) cloudy???
Water changes are done weekly, all filters are well established, all water 
is within the 6.5 - 8ph level (have a cichlid tank too - also breeding) 
ammonia levels nil, nitrite virtually nil etc etc etc.
The fish seem fine - it just annoys the hell out of me that the tanks are 
cloudy!

"Sandi"  wrote in message 
news:43c01a3b$0$63072$ed2e19e4@ptn-nntp-reader04.plus.net...
>I have two tanks (out of my 11) which always seem to have cloudy water. 
>All my tanks  are at least 12 months old, all are established and all 
>fall well within the "good water parameter" borders". all are filled via 
>the same water supply with the same water conditioner, yet still two 
>remain cloudy. One is my gourami tank, holding half a dozen various 
>gouramis, all over 12 months old, and 2 clown loach as well as 
>bumblebee gobies - again all over 12 months old.
> The other is a small tank originally kept for breeding killies in, that 
> currently holds a fairly ancient angel fish and 4 baby (2 month old) 
> danios. Plants grow well in both, the gravel is well vacuumed every so 
> often in both, here's definitely no dead fish - so why are they, and 
> none of the others (cold water and topical) cloudy???
> Water changes are done weekly, all filters are well established, all 
> water is within the 6.5 - 8ph level (have a cichlid tank too - also 
> breeding) ammonia levels nil, nitrite virtually nil etc etc etc.
> The fish seem fine - it just annoys the hell out of me that the tanks 
> are cloudy!


Post your buffer (or alkalinity, kH).  It sounds like a bacterial bloom, 
and many bacteria do poorly in very acidic water.  If you have a low kH, 
then your pH might be bouncing up and down through their threshold 
(worsened by water changes in this instance), so the bacteria alternate 
between multiplying and dying off.  Solution is to do a major clean 
gravel vacuum and several water changes in a row.  If your source water 
is naturally low in kH, then baking soda or calcium leeching minerals can 
be added for stability.

Other ideas are more conventional, such as filter types, age & porosity 
of filter media, fish-load, diet (carnivore's diet is typically more 
polluting than a vegetarian's), temperature (absolute and daily 
variation) etc, but my money is on being at the threshold of old-tank 
syndrome and your kH is exhausted.

Very often, adding a 2nd filter solves the problem of fish growing and 
filters not ;~). hth
-- 
www.NetMax.tk

NetMax wrote,
>but my money is on being at the threshold of old-tank
>syndrome and your kH is exhausted.

My first thoughts also, but Sandi might not know what Old Tank Syndrome
is/does! Toxic ammonia becomes non-toxic ammonium in low pH, and some
ammonia test kits will only measure ammonia, not ammonium. The bacteria
on the other hand, don't know the difference. If eather one (ammonia or
ammonium) goes up quickly for any reason, the bacteria colony will
bloom. Cloudy (milky colored) water is a bacteria bloom. The cause of
the bloom could be one of many things which you (NexMax), has already
pointed out............. Frank