Older tanks can deal with diatoms better than new ones. The idea that in a new set up, diatoms are guaranteed is wrong.
Sorry I can't advise you better on how to dim it, do you have any pictures of what the unit looks like? Maybe electrical tape over every other LED?
Sorry I crossed posts with you there!
Its just a little fluval chi (19 litre) Here's the tank, a day after cleaning. Three days later lots of the java fern surfaces are coated in brown diatoms.
http://i.imgur.com/eq3x9Zs.jpg
Hopefully the insect screen will help. If not I think my options are limited!
Otto's will eat diatoms. Couple of weeks after starting my high tech tank, brown diatoms appeared, despite keeping light levels low. Bunged in a couple of Otto's and they scoffed the lot in a day or two. You could see the munched tracks through the diatom layer where they had been busy.
Or just leave, frequent cleaning and water changes and they will go away.
Hi
I got some problems with brown algae some months ago with this same filter/light Eheim combination (Aqualight + Aquacorner filter)... I finally realized that it was not a problem of light intensity (it is a low to medium light) but a problem of the filter design. The inflow of this filter is a large sponge (compared to the filter volume) that covers all the front and creates a very gentle inflow, perfect for shrimps. But the problem is that plant debris remain at the surface. You will have noticed for sure that when you remove the filter from the tank to clean it, lots of debris end up floating in the water. And sometimes when you switch on the filter again, some of the debris that were still on the sponge are released again. As a result a significant load of organic matter is always floating in your tank/subatrate/corners.
Frequent and very large water changes helped a lot (twice a week and sometimes changing 100% of the water... thus nearly two changes in one) but I finally changed the filter. Now I am running an external filter (JBL e401) which delivers a perfect flow and I can get rid of all the debris with just one weekly 50% WC. IMO it is a filter designed for having very few plants (not densely planted tanks) and shrimps. Or at least for advanced aquarists whose plants don't melt... Not impossible but you suffer quite a lot.
Jordi
Thanks Jordi thats useful. I haven't noticed that yet as the filter itself has only been in there for just under 3 weeks, and I've been avoiding cleaning it so as not to disturb bacteria as it establishes itself. I will keep an eye out when I remove it for cleaning. I am hoping there won't be too big a problem. Did you try running it with just the internal canister (they call it the "mediabox") and no sponge?
No, I always run it with the sponge and the mediabox... I didn't notice you had it for just 3 weeks. As mentioned diatoms can be there due to an immature bacteria colony, but try to avoid the problem I mentioned in the coming months, additionally to brown algae it is quite frustrating to have all this mess floating around each time you touch the filter, and in my opinion this filter should be cleaned quite often as the sponge gets clogged very easily. Even in my canisters in have a sponge in the inflow to prevent debris from entering to it, and I rinse the sponges twice a week... And believe me, they are plenty of debris.Thanks Jordi thats useful. I haven't noticed that yet as the filter itself has only been in there for just under 3 weeks, and I've been avoiding cleaning it so as not to disturb bacteria as it establishes itself. I will keep an eye out when I remove it for cleaning. I am hoping there won't be too big a problem. Did you try running it with just the internal canister (they call it the "mediabox") and no sponge?