I understand your concern with keeping debris out of the filter. While Eheim does recommend using the enclosed foam prefilter on the intake strainer (as nc_nutcase) suggests, Eheim says to only use it for about 6 - 8 weeks to allow the bacteria strains in the filter media to perform their biological & mechanical filtration.
I have been using the 2229 model since Dec. 2004 on a lightly fish-stocked and moderately planted tank. I haven't noticed any excess accumulation of debris, as compared to an Eheim 2217 or 2260. Occasionally some plant material gets sucked into the filter and sometimes clogs the intake port of the filter, but that rarely occurs.
I do keep the intake strainer about 5 inches above the sand substrate to reduce larger plant parts from being drawn in. I also have an Eheim 2028 on this same tank to provide additional mechanical filtration.
I clean the 2229 about every 6 months. Since I have untreated well water for my water source, I typically thoroughly rinse 2 of the 3 media baskets to flush any debris from the basket, keeping the 3rd media basket in a bucket of old tank water during filter maintenance. Then clean the rest of the filter, including the impeller cavity & other filter internal parts. Once a year I clean the hoses.
I haven't noticed any ammonia or nitrate spikes this way but then again, this is NOT the only filter on this tank and I do have sand substrate, rock decor & the tank is moderately planted with a low fish load.
I definitely agree with what nc_nutcase says about keeping the biological media clean and I have stressed this in other posts I have written. If you are more comfortable keeping a sponge prefilter of the intake then do so. But you will have to clean that prefilter more often so as not to reduce the ability of the filter to have sufficient water available to operate properly.
Hope this clarifies things a bit.