Weirdly, I didn’t get a notification for this! — I found my own way to the party!
Perhaps the hashtag messed it up?
This isn’t an unreasonable fix! The major concern will be the mating joint between old silicone and new silicone, in the bottom corners of the replaced pane!
The tank is short enough that you could probably get away with it… however, I think you’ll have much better results if you also add a little triangle of glass to each of those inside corners during the pane swap!
You can get these right triangles of glass out of the corners of your broken pane, don’t make them very big though! Maybe 1” max leg length…
Why keep the glass triangles so tiny?
— standard aquarium silicone is Room Temperature Vulcanizing (RTV), and requires humidity from atmospheric air to actually cure! This means a large slab of silicone laminating two pieces of glass together, face to face, will take an extremely long time to cure, and may never cure if any one edge of the silicone is too far from the center! (You can expect a silicone cure rate of around 1mm per-day after the first ~14mm of depth… so, a 1” leg length triangle that’s <=1/4” thick can take upwards of 3 weeks to fully cure out if laminated down to tank bottom and vertical panes!)
(The idea here being to bridge the questionable new/old silicone interface with a large surface area of fresh silicone in a strong glass:glass bond!)