Thread: Fibreglass tank

Hi all I am new to this forum.
I hope to pick your brains if I may.
I have a few koi at the moment in a small raised sleeper pond which I built 3 years ago it holds 1200 litres, and has a pressure fed system on it at the moment.
I have just acquired a 500 gallon fibreglass tank from where I work.
I purchased an easy pod air and a 15w uv, ready to plumb in.
I want it gravity fed.

Q1: what size bottom drain would be best?
Q2: What size return pipe?
Q3: the inside of the tank is grey is there any drawback in having it grey?
Q4: could it be painted black if so what product would be suitable?

The tank as 2 ribs running around it, I am thinking of cutting between the ribs and putting a viewing window in, and insulating and cladding the sides.
What are your views on this.

Thanks for the reply, but I started to clean the tank out and noticed that the gel coat is crazed in some places.
So that's buggered that plan up, might just buy a EZ pond 500i or build a bigger sleeper pond.
The cost of the materials to build a sleeper pond would be about the same sort of price of a EZ pond.

One thought is that if the flow velocity through a pipe is too slow, crud will precipitate out and form a sediment on the bottom of the pipe.
With a 4" pipe that equates to a flow rate of about 20k litres/h.

That said, if the pipe is fairly short, it may be easy to clean.

I put a pressure wash drain cleaner* through mine from the filter end once a year or so, and the crud that comes through into the filter is amazing.
* One of those with backward facing jets, so it pulls itself down the pipe.


So, as Alburglar says, 4" is possibly overkill.

Thanks for the reply
I would but I was going to put a window in aswell, but thinking it's going to be a lot of work that I might not be up to the task.