I have used the EcoPlus pump for the last two years, I run it during the winter with success if you can find them. Bought them off eBay. Here it is on Amazon http://www.ebay.ca/itm/ALPINE-CYCLONE-PUMP-8000-GPH-WATERFALL-POND-PUMP-/220762874321?pt=LH_DefaultDomain_0amp;hash=item33667e21d1#ht_1091wt_92 I also have a Alpine Cyclone 8000 pump if you need something with kick. I have to push water 50 feet uphill and this works nicely? I run his one in the Summer, creates a lovely noisey waterfall. http://www.ebay.ca/itm/ALPINE-CYCLONE-PUMP-8000-GPH-WATERFALL-POND-PUMP-/220762874321?pt=LH_DefaultDomain_0amp;hash=item33667e21d1#ht_1091wt_92 Here is a link that might be useful: EcoPlus 4950 Gallon Pump

Old topic but wanted to share my input. I'm growing hydroponic tomatoes (various strains) at university in a lab setting (indoors under HID lights) and outdoors in a greenhouse. In one of my greenhouse NFT systems, i recently had a similar problem on 1 tomato plant (total 9 plants that share the same res and tubes). But im gonna try to diagnose your issue by mentioning what others missed out on. 1 major cause of leaf curl is compaction of root system (i.e. roots are compressed or dont have enough space to expand). This risk is exacerbated in hydroponic systems that use tubes. This was the problem i had and had to replace tubes with square tubings that have a liftable top. Once you have access to roots, you must seperate them strand by strand (i.e. so they arent sticking together). In your setup, this risk will further be exacerbated because you filled the entire pvc tube with hydroton (right?). Remove hydroton from tube and place the plant in a net cup with hydroton. Nitrogen burns usually cause browning/yellowing of leaves (similar to sun/heat burn) and not purpling. Test your solution for each chemical if possible, or use a commonly employed aggregated measuring device that shows total concentration in ppm (dont let it exceed 2500). In my system, only one plant was affected. Coincidentally, it was the largest of all plants with the most root mass. I let another normal one grow to its size to see whether it would undergo the same problem, and it did. Viral and bacterial infections that cause leaf roll usually cause it to roll up. Same with the physiological roll. If your leafs roll down AND if your stems bend, this is caused by a diminishing turgor pressure (read: not enough water reaching afflicted area). Mist several times when lights are off (no photosysnthesis) and observe increasing turgor pressure (unbending). Or, untangle roots and remove hydroton from from pipes. I tested various growing methods including fully and partially submerged roots. They all work but a submerged root cannot intake oxygen; it has to borrow oxygen from another part of the plant (i.e. a root part that isnt submerged or above ground stem). This requires energy for transportion and isnt the most efficient (optimal) way for growth and cellular processes. Lastly, an airstone in the reservoir is useless unless the reservoir is completely airtight all the way up to the plant holes. Better to keep small airstones in the pipes right under the plant roots. Those that say aerating the res prevents bacterial development.. is false. If you dont have air in res, you will get anaerobic bacteria (they grow/accumulate slowly but acidify the solution); if you have air in res, you get aerobic bacteria (not acidifying but grow extremely fast). Most bacteria prefer aerobic environments for optimum growth.

Update: I installed a Zoeller M98 and replaced pipe on inside of house and check valve two days ago. Then ran it to 25' of 2" pipe on the outside to 25' of 1 1/2" pipe and then ran a hose from that about another 30' away from the house. The time between cycles is starting to increase. When I first installed it, sump pump ran ever 10 minutes. Now it's running about ever 40 - 45 minutes.

There are far better sump pumps than HD sells available. Try a pedestal type with a US made motor. Having an oversize pump can cause failures from excessive short cycles.