Base diet first. Feed either a good rat-specific dry mix or a formulated lab block as roughly 80-90 per cent of the diet. A good mix is varied, low in fat and sugar, and does not rely on seeds or coloured pieces. Blocks guarantee balance but are dull; many keepers use blocks plus a mix, or a mix plus a daily fresh portion. Protein sits around 12-16 per cent for adults, a little higher for growing youngsters, pregnant or nursing mums, and some elderly rats. Fat around 4-5 per cent. Too much protein and fat is a common cause of itchy skin and scabbing in males. Fresh food daily, in small amounts: leafy greens, broccoli, peas, carrot, cooked sweet potato, squash, herbs, small pieces of apple, banana, berries or melon. Cooked egg, plain cooked chicken, mealworms, plain yoghurt and a little oily fish are good occasional protein. Sexes differ a little. Males do better on lower protein and fat; females are usually more active and tolerate a bit more. Older rats often need softer food and a closer eye on weight. Avoid free-feeding an overflowing bowl. Rats selectively pick the fatty bits and leave the rest, which unbalances the whole mix. Give a measured portion and let them finish it. Fresh water always, changed daily, from a bottle with a working ball bearing plus, ideally, a heavy bowl as a backup.