Awesome looking tanks. Ive sen these vases before and I think they also come in 8" and 10" sizes as well. For filtration maybe you could get an Eden 501 type filter and split it between the two tanks ? You could use airline tubing for the inlet and outlet and you wouldnt need a spraybar or anything in such small tanks. Boyu make a Eden 501 type knockoff that is rated for about 150 or 200 lph, maybe you could try that if you think the eden would have to much flow. I think its called the EF 05.