Anthony
You realy need to get a water storage tank.
Having a small system isn't a problem as long as you realize that your tank will not be as stable as it could be, which means more regular water changes.
I was lucky because my Father Inlaw is a manager at Bailey Tanks LTD so at the end of a run they made a 1000 litre tank for me.
To the discust of many people here as well as my main tank I have a two foot tank with a couple of clowns in it (according to someone I also have an anemone in there as well but I don't remember putting one in their).
I keep this tank very stable by doing regular but small water changes. but this can only be done if you have the water on hand.
Your tank is not anywhere near as small but you could benefit in the same way if you get a storage tank and change your water more often.
Aaron