Diddy, use Citrus fertilizer..If you can't find it locally, check out Ebay..There's a nusery, I believe it's Sunshine Nursery that sells citrus fertilizer.
Fish fertilizer isn't enough for citus needs.
Sun is important too. Set your Calamondin in the sunniest part of the house. Then outdoors weather permitting..Toni

I use Peters Professional mix for acid loving plants, or MirAcid. Both are widely available. I mix about a half teaspoon per half gallon and fertilize every two or three weeks during the winter, spring, and fall (less in the summer, since I am away!). I agrees with Hopeful that sunlight is important. Your Calamondin should set fruit reliably, without any need for pollinators, so the fact it hasn't suggests it is somehow unhappy. The most likely cause is poor watering.

Watering before the tree gets stressed is crucial, since stress can cause fruit drop. My Calamondin, like some of my other citrus, shows early stress by slightly curling its leaves (from the edges in toward the center, so the leaves almost begin to look like they are trying to turn into cigars). When I see this, I know I have gone at least a day too long between waterings.

Temperature should not be an issue: trees in citrus groves endure extreme variations in the spring months, and still set fruit reliably.

Light intensity may also play a role. And possibly the lack of pollinating insects, but I think Calamondins set fruit relatively reliably indoors.

Good luck!

Don