Best is to just skip the feeind till you get back.Dont use the blocks,more bad stories about those than good ones.If you have someone you trust,you can lay out premeasured portions for feeding but thats more risky than no food
yep no food is better than food blocks. I heard, don't know if its right, that the blocks are actually chalk with the food inside. They do turn water cloudy and horrible and I have alot of people come in saying the block didn't dissolve at all aswell.
I have been away for a full week in the past and didnt feed my 50 Gal community, and i came back to a sparkling tank. Plus it is true, in the wild they do go days and weeks with no food, so for 4 days... it will probable do them good as they will scavange the tank and eat all floating particles and loose algae.