been having prob with keeping deep gravel clean...
Answers:
You might want to look into Malaysian trumpet snails (Melanoides tuberculata). They are a plauge snail but generally will not exceed the amount of food. They hide in the substrate during the day (nocturnal), eating debris in there. They also aerate it so if you have a sand layer it will be very good for that. They do not eat plants unless they are decaying already. Some people do have issues with plants that have shallow root systems because they move the gravel around a lot, causing shallow rooted plants to float. You can buy them on ebay, 50+ for $10 or a local pet store may have them for free.
With the small individual sizes of the better plant substrates, this can be a challenge. I usually use the venturi-type siphon devices to clean substrate... Just turn the water flow down at the faucet. If this is unreasonable in your case (High plant load) you might want to try Golden Clams (Corbicula fluminea).
Alternatively, by having a planted tank, you can get away with allowing the detritus and waste to accumulate more so than with a non-planted tank allowing the waste to serve as a natural fertilizer. (Pretty low-tech, but some people do it.)
