What causes this? I've suddenly got lots on the floor, turtle island and rocks....I've never had it before, the only two things I've changed is - two new uv tubes and a live plant (weed) different one to what I had before (never had algae with previous weed). Would it be either of these thats caused it? What can I do to solve it?

i would guess its the new tubes Dawn.obviously your old ones werent putting out sufficient uv to promote algae growth.you would get the same effect should you put the tank in direct sunlight.if this was a fish tank i would keep a group of fish that consume algae.im not sure if this is possible wih turtles.

It would be the light... and probably the excess nutrients in the water from feeding the turtle and turtle waste. You could add a few more fast growing plants and see if they take up the excess nutrients.

After googling 'brown' algae, (which is what I've got apparently ) it says its to do with the nitrates/nitrites. I have checked my water levels - and everything is at the correct level apart from the GH but then our water round here is hard so thats to be expected. However I have done a small water change and will see if that helps. I am wondering if its the new filter? Cos the bottom isn't as clear as it was (as in there are small bits) I never had this with my other filter? At the moment it's not a problem - more disappointing as not had this till now

As for the lights, it says that if you have algae than to increase the lights but my lights have increased in the sense that I have new uv tubes.

The only good thing is it's easy to clean off, but would still rather not have it at all

It is the new filter as it sounds like Diatom Algae as it's easy to wipe off. It is very common in a new set up and to put it simply...
Diatoms usually appear when an newly setup aquarium filter has finished the nitrogen cycle process... due to excess silica/silicates from tap water sources.
It's just the tank settling down, wipe away what you can. It usually disappears a quickly as it came. Try not to overfeed or keep uneaten food in the tank though as this will slow the process.
Just a tip never increase light when you have an algae outbreak. Algae is a plant, but much less complex than aquarium plants. It will grow with much less nutrients, whereas a plant would struggle. Let's say phosphates and nitrate but insufficient carbon, if you were to add more light the algae would thrive. Whereas as plant wouldn't

Thank you Anita, that does sound plausible as never had a problem with other filter. I set up the filter as it instructed - it said to was media with tap water initially then when you wash it in future to use tank water. I checked all the levels and everything is still ok, so will leave it alone for now and hope it disappears.

Keep an eye on your phosphates, nitrites and nitrates. Brown algae occurs when there is a drop in water quality. Do you test frequently?

I base my knowledge on many years of keeping several fresh and salt water aquariums, so please consider your turtles of which I know nothing. In the first instance cover the tank with newspaper, turn of the lights and don't feed the turtles for a couple of days. The fish are fine in the dark and food less for a few days , would your turtles be? The longer you can do this for the better, I've done three days for the marines as I'm concerned about my soft corals but the fresh water tanks can stand it for longer. This will make a huge improvement in the algae, in fact depending in how much you have it may cure it. Next you need to prevent it from returning. WARNING - I know nothing about turtles, just water quality - if the turtles can stand it do a decent water change, maybe 40%, then do a 10% water change twice a week until problem is solved. Long term the only answer to preventing algae is to test water quality weekly and repondtothe results, correcting any thing You find. Also consider your stock to water ratio - too many turtle for the volume of water/ size of filters s a major contributing factor to the poor water quality that causes algae. another major cause is over feeding/ not removing uneaten food.
Hope that helps x

Hi Clare,

Thanks for your reply, funny enough I tested my water tonight. It is, as it's always been fine. The only level I have problems with is the water hardness but even thats within normal range. Nitrates, nitrite & ammonia levels are all perfect (according to the test strips!!)

I think its the other stuff mentioned above not brown algae now, despite my overwhelming urge to clean the filter (the outlet flow has slowed a bit) I am going to leave it a bit longer so that the filter has time to settle. I will aim to clean it this weekend. I had no problems at all with algae until I got the ne filter so do believe this may be the cause - I will soon find out! It hasn't got any worse at all, so am hoping that now it will start to disappear.

This weekend I was thinking of doing a 90% water change so that I can clean the slate on the bottom of the tank and will probably replace with some of the tank water as well as fresh water. I will also clean everything in the tank water instead of tap water - inc the filter. The water as a whole seems to be quite clear.

The other option is to do a 40 - 50% water change and just take everything out so that I can try and clean the slate before placing everything back.

I topped up the water and turned the thermostat down this evening as I'm finding the water evaporates really quickly

If it's the new filter cycling then changing water and cleaning things will not allow the filter to cycle. The best thing to do would be ride it out a bit longer, the filter will cycle and the problems should resolve them selves. If you clean it out now you will risk losing any of the good bacterias that are left in the system. X