thanks.

BTW, you had algae primarily because of water level dropping due to evaporation, but also probably too much oxygenation. That pump is too big and unsteady for the container.
Also, algae shouldn't grow in water. What nutrient level did you add (ppm?)? is it chlorinated water?

Chlorinated water doesn't grow algae, and algae doesn't tend to grow because water is "too oxygenated". While it's theoretically possible to over-oxygenate water, that's not what happens when you get algae growth.

Oxygen levels that are too high will kill plants (as oxygen is actually lethal to all life at high enough levels). Practically speaking unless you're dumping concentrated H2O2 into the water or you're bubbling pure O2 into it at an alarming rate, you're never going to over-oxygenate your water.

But O2 in water KILLS micro-organisms like algae. That's one of the two main reasons we aerate water in hydroponics (the other being that the roots have to have O2 available).

freemangreens is absolutely correct in the cause of the algae - light. Heat helps, but light is the big one. Algae won't grow without light and rooting is actually improved in most plants by darkness, so you always want to make your cloners light-tight.

That brick is also a good possible culprit for the quick onset of algae... it probably had a lot of micro-organisms on it when it was put in there. That's a very hard thing to clean.

Anyway, my guess to the cause of your problem, childswonder, would be inadequate aeration/flow. Pictures would help out a lot here. Honestly, the simplest cloning method involving any kind of hardware (ie more complicated than a glass of water) is what's called a "bubble cloner". Same basic principle as freemangreens' system but you build it flat and short, like one of those plastic under-bed boxes and use an air pump with several airstones to move the water. Those things have insane success rates for me.

If it doesn't look like your water is boiling, you don't have enough air going into the water. Check out the principles of aeroponics. You can't over aerate.

To clone I put cuttings in plugs. I do use a rooting hormone. The plugs sit in cells. The cells sit in a shallow nutrient solution with a humidity dome. When the water level is low, I add some solution by hand. That's it. I have nearly 100% success rate out of tomatoes and basil. I can't understand the appeal of going high tech on something when low tech is just as good. If my plants don't have good roots sticking out of the plugs in two weeks, I replace them. Rarely is that the case. Aero isn't any faster at all in that stage. They say you have visible roots in days. Of course they're visible without a plug. The low tech way produces roots in days, too, except that you can't see them because they are growing in a medium. But they aren't ready to plant for some time later and the plug allows the plant to start anchoring into something from the get go and completely simplify the process of transplanting. Also, the plug is a good measuring device. If your roots are long enough to be sticking out in several spots, then they are long enough to handle transplanting.

I know I didn't answer the questions, but I felt like sharing.

Well the basis of a bubble cloner isn't exactly high tech. It's just an air pump and a water bath.

And if you're planning to stick with hydroponics or aeroponics, rooting without using a plug is more versatile to transplanting into hydroponics. You don't have to worry about whether the plug fits nicely, whether bits of stuff will get into your system, etc. It's just a plant with bare, clean roots.

It's really not complicated at all.