The fish are healthy, I do not overfeed them, I often skip feeding them for a day each week so they can digest the food. I give the fish Daphnia and Bloodworm every so often, I have a light and I turn on the filter and bubbles for sometime everyday, but it just seems to get dirty really quickly.

I change some of the water weekly [20% about] but nothing seems to stop the tank getting dirty. I have natural non-coloured gravel which Iwash [with boiling water through and through and also cold water] when I clean the tank, and the tank has a lid which is open all the time letting in a fresh supply of air.

Also, I have another smaller 20 gallon in which I have eight very very tiny fish [taken from my pond, they are about max. 1.5 cm long]. I was wondering if you could tell me approximately how old these fish are?
They are still the dull grey colour, but I took them out of the pond because they were getting eaten by the other big fish, and I intent to place them back in the pond when they are bigger, I will not keep them in the tank if it gets too small for them, but right now they have more than enough space, and plenty of plants, a bubble machine, rocks, natural gravel, and air supply, and 15-20% water change every 2-3 days, as I feel a filter may suck them up!!

However, I am going on holiday for 2 weeks in about a week and a half, and was wondering about both tanks, as a site I visited advised me against feeding blocks, or feeding at all!
It said not to feed the fish if your holiday is under 3 weeks.. However I have someone come in and feed them usually. Is this ok? Or are feeding blocks really that bad? I understand fish can go for a long time without food, but I am unsure about if I should just leave them.

I also do not know what to do about the little fish, as I would like to raise them for a while. Would you say it would be ok to leave the little ones in that tank and ask the person to feed them once a day and change some of their water every so often, or would it be kinder just to put them back in the pond? Their tank is clean and safe, and our pond is pretty disgusting [we are building a new one currently]. Goldfish are pretty hardy, and living in our pond outside when they were tiny; I would say they can cope in a nice clean tank for a few weeks with feeding, but I would like another's advice!
Thanks for reading, sorry it's a lot of writing, but hopefully you could give me some advice! Lissie

You should let your 30 gallon tank have a chance to settle down.
With such a small number of fish in the tank you needn't be overdoing the cleaning.
Also you should leave the filter running all the time as every time you switch it off much of any beneficial cleaning bacteria inside it will die and have to re-establish themselves once you turn it on again. It takes several weeks for a full bacterial colony to establish, so you're hardly giving them a chance!

Incidentally, if you rinse out any sponge filter material always do it in some aquarium water rather than fresh tap water (the tap water will also kill off bacteria in the sponge, but tank water won't).

Goldfish are messy creatures, always digging around in the gravel and this is what is keeping your tank dirty. You can remove any silt built up in the substrate (glad you're not overfeeding!) by siphoning it with a 'Gravel Washer' - just a wide bore funnel thing that lets water and silt out but not the heavier gravel - when you do your partial water changes.

Keep the lid of your tank shut. Not only will this keep dust out of the water but it will also safeguard against the fish jumping out! With your bubbler working, there's no risk of the fish suffocating.

OK, now for holiday time. Feeding blocks always seem too big for the job and they could pollute the tank.
As your fish have been fed normally on a full varied diet for some time then they can indeed be left unfed for up to two weeks whilst you're away. If you want to trust a friend to feed them, make up portions of food (the same amount that you normally feed each time) in small twists of paper and get the friend just empty each twist into the tank at feeding time.
You could ask your friend just to feed every other day to make sure the fish aren't overfed by a generous neighbour!

It sounds as if your fish are youngsters from this year's spawning in the pond.
They may be around a few weeks or two or three months old. They're fortunate they didn't get eaten by the bigger fish in the pond. Keep them in the tank perhaps until next year and then only release them into the pond when the water temperature is fairly warm (say May or June). Again, you could let your friend give them just a pinch or tow of food every other day to keep them thriving whilst you are away.