Filtration in 55 Litre

[SushiLuckyFin]

I've got a few questions regarding filtration.

I have a 55Litre (12.5g or there abouts) with two goldbabies. a fantail and a lionhead (YES!!! I will be upgrading to bigger tanks when required, prob 110L or so some time next year. So please, save me any lecture, I have done LOTS of research on the subject and they are still babies... aww)

I cycled it fish-in, (after researching for two months beforehand!) and it only properly finished cycling once I put the Aquaclear 200 from my fluval 6g on in addition to the Aqua One 100F-LV (150L/hr flow rate) that the LFS employee told me would be more than adequate. He advised me AGAINST spending MORE money on a bigger filter. But I realised it probably wasn't enough by the way the cycle was going, so figured i'd stick the filter for my new tank not set up yet on there. Voila, cycle finished within a week! That was two weeks ago.

So...

now what filter to put on it. can't do HOB filter, there is no space at the back for it to go, the one on there obscures the view and looks ugly, and will need to go in my new tank once it's set up. and looking at filters I can get over here (Australia) they are either 40L (400L/hr) or 70L (700L/hr), I bought a new Aqua One internal filter for tanks up to 75 L, 450L/hr flow rate, and the current is, well a little strong! and it's not adjustable. I was looking at a Blue Planet internal Filter, but it only comes with venturi outlet! WTF??? So at the moment I have AquaOne 102F internal filter (450L/hr) PLUS Aquaclear 200 (waiting for delivery of the rest of the stuff I need for the fluval Edge)

How much flow rate do you ACTUALLY need??

Another thing, is now the tank has cycled I thought the water might start clearing up, it is still SO CLOUDY, like milky cloudy. Parameters are spot on (API liquid tests)

Ammonia 0ppm
Nitrite 0ppm
Nitrate 20ppm
Ph 7.4
Temp around 18C

This is just before weekly routine PWC of 20%. And I gravel vac every water change.

I'm wondering if popping a carbon cartridge in the Aquaclear for a few days might help? or would it do more harm than good? I'm loathe to use it unecessarily (as with any other chemicals)

I also still have diatoms... everywhere... as it is only where the light reached (there are clear patches on leaves where shadows are cast by other leaves) I am now on day 3 of a 3 day blackout. There don't seem to be any visible changes. I had lights on timer 7am-7pm previously.

Um, trying to think it there's any other info I can give that I might have missed...

Sorry if some of this didn't make sense... so many factors at play ARRRGH!!!

 

[Laser]

It sounds like you are doing well. I'm not used to thinking in liters, but it sounds like you have enough flow rate for the moment. It's almost impossible to over-filter, especially with goldfish, but since they are babies you don't want the flow of the water pushing them all around the tank. Ideally you will want 10 times the flow rate of your aquarium capacity, so right now you'll want to be filtering about 550 liters per hour.

I have a single goldfish in a 75 liter tank and I have an aquaclear on it that filters 1135 liters per hour. That's a 15x flow rate and I think that is something I would shoot for once your goldfish get a little bigger and can swim against the current.

Edit: I would save the carbon for when you actually need it to remove something from the water.