cloudy water

I have 4 fry tanks next to each other, all running on sponge filters, they are all different makes/lighting, but one of them has persistent cloudy water. Could it be a bloom of some sort? All tests are fine, and the fish are too, its just that they don't look very pretty!!

Any suggestion what I can do to clear it? Would leaving the lights off for a few days help? They're currently on for about 6 hours.

What colour cloudy, grey or green?
Same gravel in each?
How big is the tank? what size & how many fish in the affected tank?

Its 60x30x30

I guess it has about 40 to 50 20p sized fry

Its bare bottomed, which gets wiped every water change, it has a 10x10cm sponge filter, I guess its grey cloudy, not green, looks like dust suspended in it when I get close up with my glasses on!!

The other tanks are all bare bottomed, same filters, although some slightly smaller, the others have old fluorescent tubes, perhaps a slightly pinkish tinge to them, and one has some leds in a strip/tube, but I think slightly underpowered for the size of tank. The problem tank has an Aqua one daylight tube.

Grey would suggest a bacterial rather than an algal bloom. you say all water quality is fine, have you checked your KH and pH?

PH is 7.6 and KH is 11.

I have horrid Thames water here, which is very hard, I do use RO water with my water changes.

If its bacterial what should I be doing??

bacterial blooms are usually caused by the beneficial bacteria which inhabit your filter. They normally attach to surfaces, both the filter foams and other surfaces in the tank such as gravel, plants, glass, etc. The bacteria multiply to a population level where they are able to break down the organic waste more or less instantaneously, that's the point a tank is considered to be mature and the nitrite & ammonia levels reach zero. If however the amount of waste produced is sufficient to support more bacteria than there are surfaces available for them to live on, that's the point you see a bacterial bloom and clouding of the water. There are other possible explanations, such as precipitation of minerals or fine particles from your tap water; but to be honest, I'd be thinking about either increasing the surfaces available for the bacteria, i.e. add another filter or possibly some gravel. Or reduce the biological load by reducing feeding &/or number of fish in the tank.
To be honest, I don't have much experience with running bare bottom tanks as I prefer to run tanks with fine quartz gravel at the bottom, my feeling is this helps stabalise the tank water chemistry & provides extra surfaces for biological activity.
One thing to watch out for though is signs of bloat. I have noticed that bloat can be associated with a distinct haziness to the water. Assuming none of your fish are looking fat or stressed (stuck in the corner, breathing hard, looking slightly fat/pop eyed, don't worry, but if you see any such symptoms :-
1. stop all feeding
2. do daily water changes and thoroughly clean the base of the tank.
3. treat immediately with octozin.

Thanks Rob your comments are so helpful! I must owe you a fortune in consultancy fees!!

No problem

bridgegirl99 wrote:Thanks Rob your comments are so helpful! I must owe you a fortune in consultancy fees!!

That is the beauty of forums....sharing the wealth

Well I've put in another filter and a plastic (yuk) plant and its already looking better, so here's hoping