Algae Bloom

One thing to try before resorting to UV is a 3 day total blackout. This means not just turning the lights off but wrapping the entire tank with something that won't let light through and leaving it there for 3 days. Don't even open the blackout to feed the fish.

If it's still there when you take the wrapping off, then I think only UV will work. You can get those that are like a separate internal filter but be careful. On another forum recently, a member bought one on-line that said it was for fish tanks. It wasn't, it was for storage tanks with no animal life in them. Fish tank ones must have a screen to protect the fish from the UV. The one on the other forum didn't and it killed all the fish.


You also need to work out the cause of all the algae. It is usually caused by an imbalance between the time the lights are on, plant fertiliser (which includes ammonia) and CO2. If the lights are on too long, that can cause it. Overfeeding fish can cause algae because uneaten fish food decomposes to make ammonia.
Having live plants to compete with algae also helps.

The green algae that makes the green water grows so quick that water changes (as you've noted) won't work as it just adds more nutrients.  Usually complete darkness will work as it stops photosynthesis and the algae will die off.  As a guess I'd say that curtains near to the aquarium that are usually closed were left open during your holiday, or tank lights left on, that caused the bloom.

What fish do you have in the aquarium and other live stock?  Amano shrimps will help reduce the algae numbers during the blackout.  If you have fish that eat live foods find a live bag of daphnia and dump it in.  Don't feed for a few days and the daphnia will eat the algae and the fish will eat the daphnia.  All in the dark of course.

Thanks guys.....I haven't done a full blackout, I will do this tonight. My aquarium is planted so the inbalance is baffling.

I don't want to go UV, but if it comes to that id have an external anyway.

I have 2 Cockatoo Cichlids, 6 Rosy barbs, 6 dwarf neon rainbows, 5 Ottos, 15 Amano, 2 Honey Gourami, 4 Blue Rams and 2 Stiphodon. Fish seem fine, very hungry as i've cut back the food.