Berlin air-lift 60 or 90 ??

Hello.
I'm setting up a fish only 120L.
At this time the aquarium is running with LS and LR, for about 2 weeks.
I want to buy a berlin air-lift skimmer.
My aquarium has a height of 45 cm but the water column is about 36 cm.
The air-lift 90 requires minimum 31-32cm water column.
What this means is the skimmer will stand 4-5cm above the sand and sucks water near the bottom.
With the air-lift 60 the skimmer is smaller but it will sucks water from the middle.

What is the best choice.
Bigger skimmer which sucks water near the bottom OR smaller which sucks water from the middle ???

 

You would be far far better off getting a Berlin HOB classic They do a great jib and can be used in a sump also .. Problem with any air skimmer is the Pump has to be so large and to get a good large quiet air pump is expensive.. I can tell you where to find them.. But then you have to think about the bi weekly changing of the wooden air diffusers and you have to always have on in the skimmer one in a bleach soak one in the first stage of drying and one dried and ready to be use plus a new spare .
Not to mention a F/O needs a lot more skimming .. The Berlin Classic HOB is a great skimmer I have one left from the old days Son ran it on his 150 reef last time I saw it..

Oh also for the depth the skimmer pulls from the very top 2 inches is best thats why reef tanks have to skim of the surface to the sump. Thats where all the oils from food and fish body slime go to the top.. With a Berlin HOB you can pull water from where ever you want just locate the pump .

 

I know that HO skimmers are better, but in my case i can't put a skimmer like this. I have small childs and i'm afraid that they look it as a new toy to play with.
Anyway, i have already bought (and still in its box) the airlift 60 and i'm comfused if i should replaced with the bigger airlift 90 which fits marginally in my aquarium.

 

The berlin airlifts do foam away once in a while, but either one will be only marginally helpful. If you really want an in tank skimmer, go with one of the Tunze series. I recommend the Tunze Nano Doc, as it is an in tank skimmer that will outperform many skimmers in its class that is rated for a tank your size.
TUNZE GmbH High-Tech Aquarium Technology: Catalog[predid]=-infoxunter050

I hope this helps!